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vendredi 14 novembre 2014
What is DNA
What is DNA
What Are mRNA, rRNA and tRNA?
RNA is a critical component of every single living cell in the universe. Without it, life as we know it could not exist. There are three types of RNA, each with a unique function. mRNA is used to produce proteins from genes. rRNA, along with protein, forms the ribosome, which translates mRNA. tRNA is the link between the two other types of RNA.
RNA Features
1. RNA, or ribonucleic acid, is a linear polymer of adenine, thymine, cytosine, and uracil that is created in the cell by a process called transcription, and it differs from DNA in several ways. First, the ribose sugars on DNA nucleotides are short one hydroxyl group compared to RNA, hence the name deoxyribonucleic acid. This key modification makes RNA much more chemically reactive. Second, DNA uses thymine to base pair with cytosine, while RNA uses uracil. Third, DNA tends to form into a helix of double-stranded nucleotides, with base pairs making up the "rungs" of the helical ladder. RNA can be found in single-stranded form, but it more commonly forms complex three-dimensional structures, and this feature usually serves to confer functionality on RNA molecules.
RNA Synthesis
2. RNA transcription is a process mediated by RNA polymerase, an enzyme that creates an RNA complement to template DNA with the help of a complex of proteins. Transcription is heavily regulated by promoter elements and inhibitors. All three types of RNA are synthesized in this manner.
mRNA
3. mRNA, or messenger RNA, is the link between a gene and a protein. The gene is transcribed by RNA polymerase, and the resulting mRNA travels to the cytoplasm, where it is translated by ribosomes into a protein with the help of tRNA. This form of RNA is extensively altered post-transcriptionally with modifications such as methylguanosine caps and polyadenosine tails. Eukaryotic mRNA frequently includes introns which must be spliced out of the message to form the mature mRNA molecule.
rRNA
4. rRNA, or ribosomal RNA, is a major component of ribosomes. After transcription, these RNA molecules travel to the cytoplasm and join with other rRNAs and many proteins to form a ribosome. rRNA is used both for structural and functional purposes. Many reactions in the translational process are catalyzed by key portions of certain rRNAs in the ribosome.
tRNA
5. tRNA, or transfer RNA, is the "decoder" of the mRNA message during protein translation. After transcription, tRNA is extensively modified to include nonstandard bases such as pseudouridine, inosine, and methylguanosine. By themselves, ribosomes cannot form a protein when the mRNA makes contact. The anticodon, a string of three key bases on the tRNA, match with three bases on the mRNA message called the codon. That is only the first function of tRNA, as each molecule also carries with it an amino acid which matches the mRNA codon. The ribosome functions to polymerize the amino acids linked to the tRNA into a functional protein
DNA (deoxyribonucleic acid) contains the genetic information to
synthesize all the proteins in the cell. However, DNA in the nucleus is
separated from the ribosomes in the cytoplasm where protein synthesis
occurs. RNA (ribonucleic acid) serves as an intermediary between the DNA
in the nucleus and the end protein. Three types of RNA are involved in
the process: messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA
(tRNA).
Transcription
1. Genes in the DNA are transcribed into mRNA. Eukaryotes modify the initial mRNA (pre-mRNA) sequence by removing introns (sections of DNA transcribed but not used in the final protein). The mRNA then travels to ribosomes.
Translation
2. Translation uses the code on the mRNA to synthesize a protein. Translation occurs in three stages: initiation, elongation, and termination.
Initiation
3. The small subunit of the ribosome binds to the mRNA. When a start codon (a codon is a sequence of bases that code for an amino acid) is detected on the mRNA, the large subunit of the ribosome attaches to the small subunit and matches an initiator tRNA to the codon.
Elongation
4. During elongation, the ribosome continues to match codons on the mRNA with tRNA carrying the corresponding amino acid. Each amino acid is linked to the subsequent amino acid by a peptide bond.
Termination
5. When a stop codon is reached on the mRNA, the protein is released from the ribosome, and the large and small subunits of the ribosome detach from each other.
Transcription
1. Genes in the DNA are transcribed into mRNA. Eukaryotes modify the initial mRNA (pre-mRNA) sequence by removing introns (sections of DNA transcribed but not used in the final protein). The mRNA then travels to ribosomes.
Translation
2. Translation uses the code on the mRNA to synthesize a protein. Translation occurs in three stages: initiation, elongation, and termination.
Initiation
3. The small subunit of the ribosome binds to the mRNA. When a start codon (a codon is a sequence of bases that code for an amino acid) is detected on the mRNA, the large subunit of the ribosome attaches to the small subunit and matches an initiator tRNA to the codon.
Elongation
4. During elongation, the ribosome continues to match codons on the mRNA with tRNA carrying the corresponding amino acid. Each amino acid is linked to the subsequent amino acid by a peptide bond.
Termination
5. When a stop codon is reached on the mRNA, the protein is released from the ribosome, and the large and small subunits of the ribosome detach from each other.
RNA – mRNA
RNA is always single stranded. It contains mostly the bases adenine, guanine, cytosine and uracil. There are few unusual substituted bases. Although there is a certain amount of random coiling in extracted mRNA, there is no base pairing. In fact base pairing in the mRNA strand destroys its biological activity.
Since mRNA is transcribed on DNA (genes), its base sequence is complementary to that of the segment of DNA on which it is transcribed. This has been demonstrated by hybridization experiments in which artificial RNADNA double strands are produced. Hydrization takes place only if the DNA and RNA strands are complementary.
Usually each gene transcribes its own mRNA. Therefore, there are approximately as many types of mRNA molecules as there are genes. There may be 1,000 to 10.000 different species of mRNA in a cell. These mRNA types differ only in the sequence of their bases and in length.
When one gene (cistron) codes for a single mRNA strand the mRNA is said to be monocistronic. In many cases, however, several adjacent cistrons may transcribe an mRNA molecule, which is then said to be polycistronic or polygenic.
The mRNA molecule has the following structural features:
1. Cap. At the 5′ end of the mRNA molecule in most eukaryote cells and animal virus molecules is found a ‘cap’. This is blocked methylated structure, m7Gpp Nmp Np or m7Gpp Nmp Nmp Np. where: N = any of the four nucleotides and Nmp = 20 methyl ribose. The rate of protein synthesis depends upon the presence of the cap. Without the cap mRNA molecules bind very poorly to the ribosomes.
2. Noncoding region 1 (NC1). The cap is followed by a region of 10 to 100 nucleotides. This region is rich in A and U residues, and does not translate protein.
3. The initiation codon is A UG in both prokaryotes and eukaryotes.
4. The coding region consists of about 1,500 nucleotides on the average and translates protein
RNA is always single stranded. It contains mostly the bases adenine, guanine, cytosine and uracil. There are few unusual substituted bases. Although there is a certain amount of random coiling in extracted mRNA, there is no base pairing. In fact base pairing in the mRNA strand destroys its biological activity.
Since mRNA is transcribed on DNA (genes), its base sequence is complementary to that of the segment of DNA on which it is transcribed. This has been demonstrated by hybridization experiments in which artificial RNADNA double strands are produced. Hydrization takes place only if the DNA and RNA strands are complementary.
Usually each gene transcribes its own mRNA. Therefore, there are approximately as many types of mRNA molecules as there are genes. There may be 1,000 to 10.000 different species of mRNA in a cell. These mRNA types differ only in the sequence of their bases and in length.
When one gene (cistron) codes for a single mRNA strand the mRNA is said to be monocistronic. In many cases, however, several adjacent cistrons may transcribe an mRNA molecule, which is then said to be polycistronic or polygenic.
The mRNA molecule has the following structural features:
1. Cap. At the 5′ end of the mRNA molecule in most eukaryote cells and animal virus molecules is found a ‘cap’. This is blocked methylated structure, m7Gpp Nmp Np or m7Gpp Nmp Nmp Np. where: N = any of the four nucleotides and Nmp = 20 methyl ribose. The rate of protein synthesis depends upon the presence of the cap. Without the cap mRNA molecules bind very poorly to the ribosomes.
2. Noncoding region 1 (NC1). The cap is followed by a region of 10 to 100 nucleotides. This region is rich in A and U residues, and does not translate protein.
3. The initiation codon is A UG in both prokaryotes and eukaryotes.
4. The coding region consists of about 1,500 nucleotides on the average and translates protein
MRNA From a Cell
A cell's genetic blueprint is encoded within its genetic material, or DNA. As the DNA never leaves the nucleus of the cell, in order for this information to get into the cytoplasm where other proteins and biochemical components reside, it is necessary to first transcribe the DNA into messenger RNA (mRNA or poly(A) RNA). This mRNA then becomes translated into proteins that carry out many functions of the cell. To detect or quantify very rare mRNAs, make probes for microarrays or construct libraries of complementary DNA molecules, mRNA must be isolated. However, total RNA (i.e. all the RNA in a cell) extraction and subsequent mRNA isolation are not mutually exclusive processes; the former must be performed in order for mRNA to be extracted.
Isolation of mRNA From Total RNA ..
TRIzol homogenization:
Total RNA includes all mRNA , transfer RNA, ribosomal RNA, and other noncoding RNAs. To separate these from other cellular components, the cell is first burst open to release its contents. This is done by resuspending cells pelleted by centrifuging (spinning at high speeds) in TRIzol Reagent (Life Technologies). Other versions of TRIzol (such as Ambion's TRI Reagent) work similarly.
Total RNA Isolation:
A series of centrifugations is used to separate the different components (proteins, DNA, RNA) of the cell into layers, or phases, within the suspension. The top, yellow-colored phase is composed of fat and can be discarded. The desired phase is tinted red, contains the total RNA and is retained. After performing a phenol-chloroform extraction and a series of alcohol washes using isopropanol and ethanol, the RNA can be pelleted for mRNA isolation. Add RNase inhibitors to prevent this enzyme from degrading the total RNA.
mRNA Extraction:
It is common to use a kit to isolate mRNAs, as homemade lab protocols do not generate large quantities of highly purified mRNAs. Commercial kits include Invitrogen's FastTrack 2.0 or Ambion's Poly(A)Pure mRNA Isolation Kit. These basic steps are common to such kits:
a) Mix the RNase-inhibited lysis buffer provided in the kit with up to 300 microliters of total RNA.
b) Heat for 5 minutes at 65 degrees Celsius and then immediately cool the sample on ice for one minute.
c) Mix this with 0.5M Sodium Chloride and then completely dissolve Oligo dT (oligodeoxythymidylic acid) in this sample.
d) Centrifuge this sample and recover the supernatant, which is washed several times in a series of binding and low salt buffers provided in the kits.
e) Elute mRNA several times until a kit-specified volume (e.g. 500 microliters) is obtained.
f) Precipitate the eluate by sodium acetate and ethanol precipitation. Re-suspend in up to 20 microliters of diethylpyrocarbonate (DEPC)-treated water.
g) Store at -80 degrees Celsius and check for quality and quantity by spectrophotometry.
A cell's genetic blueprint is encoded within its genetic material, or DNA. As the DNA never leaves the nucleus of the cell, in order for this information to get into the cytoplasm where other proteins and biochemical components reside, it is necessary to first transcribe the DNA into messenger RNA (mRNA or poly(A) RNA). This mRNA then becomes translated into proteins that carry out many functions of the cell. To detect or quantify very rare mRNAs, make probes for microarrays or construct libraries of complementary DNA molecules, mRNA must be isolated. However, total RNA (i.e. all the RNA in a cell) extraction and subsequent mRNA isolation are not mutually exclusive processes; the former must be performed in order for mRNA to be extracted.
Isolation of mRNA From Total RNA ..
TRIzol homogenization:
Total RNA includes all mRNA , transfer RNA, ribosomal RNA, and other noncoding RNAs. To separate these from other cellular components, the cell is first burst open to release its contents. This is done by resuspending cells pelleted by centrifuging (spinning at high speeds) in TRIzol Reagent (Life Technologies). Other versions of TRIzol (such as Ambion's TRI Reagent) work similarly.
Total RNA Isolation:
A series of centrifugations is used to separate the different components (proteins, DNA, RNA) of the cell into layers, or phases, within the suspension. The top, yellow-colored phase is composed of fat and can be discarded. The desired phase is tinted red, contains the total RNA and is retained. After performing a phenol-chloroform extraction and a series of alcohol washes using isopropanol and ethanol, the RNA can be pelleted for mRNA isolation. Add RNase inhibitors to prevent this enzyme from degrading the total RNA.
mRNA Extraction:
It is common to use a kit to isolate mRNAs, as homemade lab protocols do not generate large quantities of highly purified mRNAs. Commercial kits include Invitrogen's FastTrack 2.0 or Ambion's Poly(A)Pure mRNA Isolation Kit. These basic steps are common to such kits:
a) Mix the RNase-inhibited lysis buffer provided in the kit with up to 300 microliters of total RNA.
b) Heat for 5 minutes at 65 degrees Celsius and then immediately cool the sample on ice for one minute.
c) Mix this with 0.5M Sodium Chloride and then completely dissolve Oligo dT (oligodeoxythymidylic acid) in this sample.
d) Centrifuge this sample and recover the supernatant, which is washed several times in a series of binding and low salt buffers provided in the kits.
e) Elute mRNA several times until a kit-specified volume (e.g. 500 microliters) is obtained.
f) Precipitate the eluate by sodium acetate and ethanol precipitation. Re-suspend in up to 20 microliters of diethylpyrocarbonate (DEPC)-treated water.
g) Store at -80 degrees Celsius and check for quality and quantity by spectrophotometry.
Embryonic stem cells are obtained from early-stage embryos — a group of
cells that forms when a woman's egg is fertilized with a man's sperm in
an in vitro fertilization clinic. Because human embryonic stem cells
are extracted from human embryos, several questions and issues have been
raised about the ethics of embryonic stem cell research.
The National Institutes of Health created guidelines for human stem cell
research in 2009. Guidelines included defining embryonic stem cells and
how they may be used in research and donation guidelines for embryonic
stem cells. Also, guidelines stated embryonic stem cells may only be
used from embryos created by in vitro fertilization when the embryo is
no longer needed.
Where do these embryos come from?
The embryos being used in embryonic stem cell research come from eggs
that were fertilized at in vitro fertilization clinics but never
implanted in a woman's uterus. The stem cells are donated with informed
consent from donors. The stem cells can live and grow in special
solutions in test tubes or petri dishes in laboratories.
Why can't researchers use adult stem cells instead?
Although research into adult stem cells is promising, adult stem cells
may not be as versatile and durable as are embryonic stem cells. Adult
stem cells may not be able to be manipulated to produce all cell types,
which limits how adult stem cells can be used to treat diseases.
Adult stem cells also are more likely to contain abnormalities due to
environmental hazards, such as toxins, or from errors acquired by the
cells during replication. However, researchers have found that adult
stem cells are more adaptable than was initially suspected.
Researchers have discovered several sources of stem cells:
Embryonic stem cells. These stem cells come from embryos that are
three to five days old. At this stage, an embryo is called a blastocyst
and has about 150 cells.
These are pluripotent (ploo-RIP-uh-tunt) stem cells, meaning they
can divide into more stem cells or can become any type of cell in the
body. This versatility allows embryonic stem cells to be used to
regenerate or repair diseased tissue and organs, although their use in
people has been to date limited to eye-related disorders such as macular
degeneration.
Adult stem cells. These stem cells are found in small numbers in
most adult tissues, such as bone marrow or fat. Compared with embryonic
stem cells, adult stem cells have a more limited ability to give rise to
various cells of the body.
Until recently, researchers thought adult stem cells could create
only similar types of cells. For instance, researchers thought that stem
cells residing in the bone marrow could give rise only to blood cells.
However, emerging evidence suggests that adult stem cells may be
able to create unrelated types of cells. For instance, bone marrow stem
cells may be able to create bone or heart muscle cells. This research
has led to early-stage clinical trials to test usefulness and safety in
people. For example, adult stem cells are currently being tested in
people with neurological or heart disease.
Adult cells altered to have properties of embryonic stem cells
(induced pluripotent stem cells). Scientists have successfully
transformed regular adult cells into stem cells using genetic
reprogramming. By altering the genes in the adult cells, researchers can
reprogram the cells to act similarly to embryonic stem cells.
This new technique may allow researchers to use these reprogrammed
cells instead of embryonic stem cells and prevent immune system
rejection of the new stem cells. However, scientists don't yet know if
altering adult cells will cause adverse effects in humans.
Researchers have been able to take regular connective tissue cells
and reprogram them to become functional heart cells. In studies, animals
with heart failure that were injected with new heart cells experienced
improved heart function and survival time.
Perinatal stem cells. Researchers have discovered stem cells in
amniotic fluid in addition to umbilical cord blood stem cells. These
stem cells also have the ability to change into specialized cells.
Amniotic fluid fills the sac that surrounds and protects a
developing fetus in the uterus. Researchers have identified stem cells
in samples of amniotic fluid drawn from pregnant women during a
procedure called amniocentesis, a test conducted to test for
abnormalities.
More study of amniotic fluid stem cells is needed to understand
their potential.
Stem cells represent an exciting area in medicine because of their
potential to regenerate and repair damaged tissue. Some current
therapies, such as bone marrow transplantation, already make use of stem
cells and their potential for regeneration of damaged tissues. Other
therapies are under investigation that involves transplanting stem cells
into a damaged body part and directing them to grow and differentiate
into healthy tissue.
What are the different types of stem cells?
Embryonic stem cells
During the early stages of embryonic development the cells remain
relatively undifferentiated (immature) and appear to possess the ability
to become, or differentiate, into almost any tissue within the body.
For example, cells taken from one section of an embryo that might have
become part of the eye can be transferred into another section of the
embryo and could develop into blood, muscle, nerve, or liver cells.
Cells in the early embryonic stage are totipotent (see above) and can
differentiate to become any type of body cell. After about seven days,
the zygote forms a structure known as a blastocyst, which contains a
mass of cells that eventually become the fetus, as well as trophoblastic
tissue that eventually becomes the placenta. If cells are taken from
the blastocyst at this stage, they are known as pluripotent, meaning
that they have the capacity to become many different types of human
cell. Cells at this stage are often referred to as blastocyst embryonic
stem cells. When any type of embryonic stem cells is grown in culture in
the laboratory, they can divide and grow indefinitely. These cells are
then known as embryonic stem cell lines.
DNA replication, DNA replication or DNA synthesis, cell division Prior
to double-stranded DNA'S copy the process of. Copied new DNA strands are
almost entirely the same, but from time to time due to copying errors
çoğalmadaki excellent not (see mutation), and resulting in both an old
and a spiral new made from yarn. This semi-conservative replication is
called. DNA replication process consists of three phases: initiation,
replication and
termination
Initiation
Starting several factors alamasında replication center'What is
collected. DNA replication in the center opens, the drop-down yarns are
partially a "replication bubble" form, a replication at both ends fork
found. Each enzyme group center runs away and moves to open the DNA
strands new yarn synthesis. Enzymes involved in this stage,
collectively, the "pre-replication complex is called. They are:
Helicase: DNA leads.Primaz: Required for DNA replication RNA "Primer"
strands synthesis. DNA haloenzim: The real growth in process a
collection of enzymes that perform
The proliferation of DNA polymerase process When it comes to the end
operation parallel Due to the lack of another problem arises: yarn trim
the 5 'end of the RNA primer strand connect to not enough space, so that
the DNA polymerase Connect The end of the copy, it will be impossible.
Solution of the problem in bacteria (or prokaryoticLarda) is very
easy: The circular structure of DNA in these organisms, so that the DNA
of a "tip" there. More complex eukaryoticLarda this "clever" is solved.
Telomere Every living thing is fixed according to the syntax of the ends
of DNA, called nucleotides (human 5 'GGGTTA 3') and in this short
sequence is repeated thousands of times. Also telomerase enzyme along
with the name corresponding to the telomere repeat sequence is a short
strand of RNA primer. Telomerase DNA replication process telomere at the
end of Connect carried on their own using the primer strand extends
telomeres. Thus, telomere RNA lining Connect copy, it is possible, but
the telomerase gene to prolong the long strands of DNA strand opposite
the other remains. This is a long remaining "single strand" in some
proteins help bent DNA end in itself creates a small ring. Ring become
not exposed to enzymes break down due to receipt of single-stranded DNA
molecules. The final stage of the copying errors that may have occurred
during the synthesis of DNA is determined by reading some enzimlerce, if
you have copied the wrong nuclease defective parts enzyme called DNA
breaks, DNA polymerase then fills in the gaps.
Figure 101: DNA helix stabilization to prevent the arms from each other
leaving again dolanmalarını enzymes (HSE) fixed amounts of both arms. In
the center, showing a separation of the DNA arms.
Figure 102: After leaving the two DNA polymerase enzymes that are
missing in both halves of the arm, complete with materials present
environment.
As is known, the cells divide and multiply. So what happens to DNA as a
result of this division? There is a single chain of DNA in the cell.
However, the newly formed cell will also need a DNA. To resolve this
deficit every stage of the process occurs in a separate a series of
miracle. As a result, a copy of the DNA of the cell division shortly
before the new cell is created and transferred.
DNA to replicate itself is divided into two parts, before the mutual.
This event takes place is quite an interesting way. Structure of the
middle of the DNA molecule resembles a spiral staircase, by an enzyme
called DNA helicase, is divided into two like a zipper. Stabilization of
the helix of DNA enzymes to prevent the arms from each other leaving
again dolanmalarını fixed amounts of both arms. (Figure 101)
Now divided into two halves of DNA. Both halves of the part that is
missing in (equivalents) present in the materials is completed.
Shortcomings in the completion work is carried out by DNA polymerase.
Thus, the two new DNA molecules are produced. (Figure 102)
Match several times during the emergence of new DNA molecules are
controlled by the controller enzymes. If you have made a mistake-that
these errors are detected and corrected immediately-may be crucial.
Correct password instead kopartılıp actually brought and mounted. All
these operations are made so that at a dizzying pace, while generating
up to 3,000 digits of nucleotide enzymes in charge of all these steps
and should be checked several times by the corrections made. (Figure
103)
Produced new DNA molecule, as a result of external influences can be
made more errors than normal. This time, the cell ribosomes, DNA, DNA
repair enzymes begin to produce in accordance with the orders. Thus, the
DNA will be protected and shall ensure the continuation of the lineage.
(Figure 104)
Here is the whole day, you never know when your life to continue without
any problems in your body admirable thoroughness and responsibility
made in the understanding of the numerous procedures and controls,
measures are taken. Everyone is completely and successfully fulfill the
task. Here is the smallest number of atoms and molecules of the Almighty
Allah, the greatest of our lives and the beautiful healthy In order to
maintain a service, has given way.
Biriyse most admirable aspects of this topic, as well as the structure
of DNA that controls both the production of these enzymes, according to
the information stored in DNA and proteins, DNA is made of the orders
and control. In the center there is intertwined so great that a system,
consisting of such a system gradually becomes in any way, this is not
possible by chance. Because the enzyme is DNA to the DNA of the enzyme
to be, that is for both of the cell, membrane, there must be complete
until all the other complex organelles.
Succession of organisms so-called "useful coincidences" as a result of
"gradual" claiming to have developed the theory of evolution, as in many
aspects than the above-mentioned before that we have DNA or enzymes
that are now in the face of unanswered questions. DNA and the enzyme are
required to have at the same time, which put forward the theory of
evolution is an impossible dream of the realization of mechanisms.
Chromosomes are DNA wrapped around proteins to form an X-shaped
structure. The diagram will help you see the relationship. 1.
Chromosomes are found in the nucleus 2. Chromosomes are made of DNA 3.
Sections of chromosomes are called genes DNA - deoxyribonucleic acid (it
is the genetic code that contains all the information needed to build
and maintain an organism) Each organism has a distinct number of
chromosomes, in humans, every cell contains 46 chromosomes. Other
organisms have different numbers, for instance, a dog has 78 chromosomes
per cell. Somatic Cells - body cells, such as muscle, skin, blood
...etc. These cells contain a complete set of chromosomes (46 in humans)
and are called DIPLOID. Sex Cells - also known as gametes. These cells
contain half the number of chromosomes as body cells and are called
HAPLOID Chromosomes come in pairs, called Homologous Pairs (or
homologs). Imagine homologs as a matching set, but they are not exacly
alike, like a pair of shoes. Diploid cells have 23 homologous pairs =
total of 46 Haploid cells have 23 chromosomes (that are not paired) =
total of 23 Sex Determination Chromosomes determine the sex of an
offspring. In humans, a pair of chromosomes called SEX CHROMOSOMES
determine the sex. If you have XX sex chromosomes - you are female If
you have XY sex chromosomes - you are male During fertilization, sperm
cells will either contain an X or a Y chromosome (in addition to 22
other chromosomes - total of 23). If a sperm containing an X chromosome
fertilizes an egg, the offspring will be female. If a sperm cell
containing a Y chromosome fertilizes an egg, the offspring will be male.
Creation of a Zygote When two sex cells, or gametes come together, the
resulting fertilized egg is called a ZYGOTE Zygotes are diploid and have
the total 46 chromosomes (in humans) Karyotype A karyotype is a picture
of a person's (or fetus) chromosomes. A karyotype is often done to
determine if the offspring has the correct number of chromosomes. An
incorrect number of chromosomes indicates that the child will have a
condition, like Down Syndrome Notice that a person with Down Syndrome
has an extra chromosome #21. Instead of a pair, this person has 3
chromosomes - a condition called TRISOMY (tri = three) Trisomy results
when chromosomes fail to separate - NONDISJUNCTION - when sex cells are
created. The resulting egg or sperm has 24 instead of the normal 23.
Other conditions result from having the wrong number of chromosomes:
Klinefelters Syndrome - XXY (sex chromosomes) Edward Syndrome - Trisomy
of chromosome
A biologically important molecule, ribonucleic acid (RNA) is similar in
some respects to deoxyribonucleic acid (DNA) but has some important
structural and functional differences. There are several types of
ribonucleic acid, each of which plays a different role within the cell.
Ribonucleic acids perform several essential tasks in protein synthesis
and are involved in gene regulation.
RNA and DNA are both called nucleic acids and share a similar basic
structure. Both types of nucleic acid are made up of units called
nucleotides. Each nucleotide is composed of three molecules: a
phosphate, a sugar and a nitrogenous base. There are several different
nitrogenous bases, and it is the sequence of these molecules that allows
DNA and RNA to store and transmit information about the long-term and
day-to-day maintenance of the cell.
Although they share some similarities, ribonucleic acid and
deoxyribonucleic acid molecules are different in three important ways.
First, an RNA molecule is single-stranded, whereas DNA is a
double-stranded molecule. Second, RNA contains a sugar called ribose,
and DNA contains a sugar called deoxyribose. The third difference is
that in DNA, the complementary base pair for adenine is thymine; whereas
in RNA, the base pair for adenine is a modified version of thymine
known as uracil.
There are three main types of ribonucleic acid. These are transfer RNA
(tRNA), messenger RNA (mRNA) and ribosomal RNA (rRNA). These three
molecules are structurally similar but perform very different functions.
Messenger RNA is the product of a process called transcription. In this
process, the genetic code carried in a section of DNA is copied,
resulting in the synthesis of a molecule of mRNA. The mRNA is an exact
copy of a section of DNA that codes for a single protein. After it has
been made, this mRNA travels from the cell's nucleus to the cytoplasm,
where it undergoes a new cellular process with help from another type of
ribonucleic acid.
In the cytoplasm of the cell, the mRNA comes into contact with transfer
RNA molecules. Transfer RNA helps manufacture proteins by transporting
amino acids to the site of protein synthesis. The tRNA uses mRNA
molecules as a template for building the protein by “reading” the mRNA
molecule to determine the order in which amino acids are placed in the
protein chain. This process is called translation.
The third type of RNA, ribosomal RNA, is the site at which translation
occurs. Ribosomal RNA molecules are the site at which mRNA is translated
into proteins. Ribosomal RNA helps in this process by interacting with
both messenger and transfer RNA molecules and by acting as a site of
enzyme activity.
Other types of ribonucleic acid include micro RNA and double-stranded
RNA. Micro RNA is used by cells to help regulate the transcription of
messenger RNA, and can both increase or decrease the rate at which a
particular gene is made into proteins. Double-stranded RNA, which is
found in certain types of viruses, can enter cells and interfere with
translation and transcription processes by acting in a manner similar to
micro RNA.
It’s in your genes. That’s how scientists explain the physical
characteristics, personality traits, and behaviors which make each human
unique. The clues carried in our genes -- in the form of DNA --are now
used to determine criminal guilt or innocence, resolve paternity or
maternity questions, predict the chance of inheriting a disease or
medical condition, and even trace the long-distant ancestors of the
human family tree.
Your body is made up of tiny units called cells – as many as 100
trillion of them, according to some estimates. Within the nucleus of
every one of these cells is a set of instructions which tell the cell
what role it will play in your body. These instructions, essentially a
blueprint or recipe for building different parts of the cell, come in
the form of a molecule called DNA. Short for deoxyribonucleic acid, DNA
consists of two thread-like strands that are linked together in the
shape of a double helix.
What is DNA?
DNA is made up of four chemical bases: Adenine (A), Cytosine (C),
Thymine (T), and Guanine (G). These bases are combined into pairs –
adenine with thymine and cytosine with guanine – to make up the “rungs”
of the DNA ladder (see Figure 21.1). Each “rung,” more accurately called
a base pair, is one of three billion such pairs which work together to
provide the instructions for building and maintaining a human being –
the human genome. The exact order in which these base pairs are combined
is called the DNA sequence. Much in the way letters of the alphabet are
combined to form words and sentences, the sequence of these bases are
the “letters” which spell out the genetic code.
What is a Chromosome?
Within the nucleus of each cell, the DNA molecules are coiled around
proteins into tiny structures called chromosomes. In humans, each cell
normally contains 23 pairs of chromosomes, for a total of 46. One
chromosome in each pair is inherited from the mother, and the other from
the father. Twenty-two of these pairs, sometimes called autosomes, look
the same in both males and females. The 23rd pair, called the sex
chromosome because it determines gender, is the one which differentiates
males and females. Females have two copies of the X chromosome, one
from each parent, while males have one X chromosome from their mother,
and one Y chromosome from their father. It is the father who determines
the sex of his child.
What is a Gene?
Genes are sections or segments of DNA that form the individual units of
heredity. They are carried on the chromosomes and contain instructions
for making molecules called proteins. Each protein enables a cell to
perform its own special function. The hemoglobin in red blood cells, for
example, is responsible for transporting oxygen throughout your body.
Another protein, insulin, helps you metabolize your food. The keratin
protein is what helps your hair and nails to grow. If you look at DNA as
a recipe for creating a living thing, then genes and proteins are the
ingredients which work together to build, repair, and run your body.
The traits which make us each unique are also inherited from our
ancestors. Physical characteristics such as curly hair, blue eyes, and a
tendency for acne are all determined by our genes. Scientists also
believe that many emotional and behavioral traits, at least in part, are
influenced by an individual’s genetic makeup. Eating habits,
intelligence, a penchant for aggressiveness, and even sleeping patterns
all have their roots in our DNA.
Because genes are carried on the chromosomes, humans have two copies of
each gene, one inherited from the mother and one from the father. The
two copies aren’t necessarily the same, however. Just like snowflakes,
genes come in variant forms. These variations are known as alleles.
Different alleles are what produce variations in inherited traits. This
is why your individual traits such as hair color or blood type may not
match those traits in either of your parents.
Ribosomal ribonucleic acid (ribosomal RNA or rRNA) helps to form the
ribosome itself. Unlike messenger RNA (mRNA), ribosomal RNA does not
transmit genetic information. Instead, it combines with proteins to
create a structure that systematically transforms mRNA into proteins.
The central dogma of cellular biology is that DNA is transcribed into
RNA, which is translated into proteins. The second step in this process,
translation, is performed by the ribosome. A ribosome intercepts mRNA,
which then requires specific amino acids to make the protein for which
it contains information. Ribosomal RNA forms a complex with various
proteins in order to bind the amino acids together.
Ribosomes can float freely in the cellular cytoplasm, or they can be
bound into a membrane called the endoplasmic reticulum (ER). ER that
contains ribosomes is called rough ER. Proteins produced in the rough ER
are transported through the ER to specific destinations. Ribosomes can
also appear in different sizes. Larger ribosomes simply contain repeat
copies of the same basic ribosomal RNA.
Ribosomal RNA appears as two separate parts which operate together. They
are the large subunit (LSU) and the small subunit (SSU). The LSU and
the SSU move smoothy in tandem along the strand of mRNA they are
translating. The LSU attracts transfer RNA (tRNA) molecules that carry
the necessary amino acids.
The part of the ribosome—at the meeting of the two subunits—that does
the work of joining amino acids is called peptidyl transferase. It is a
catalyst: it facilitates a chemical reaction by creating an environment
in which the reaction can easily take place. As such, it is called a
ribozyme, and is one of the few organic catalysts that is not a protein.
Living organisms contain several hundred copies of the genes required
for the two molecules of ribosomal RNA. This abundance and redundancy
reflect the crucial role that ribosomal RNA plays in supporting the
process of life. There is no known organism on Earth that would be able
to function without rRNA.
Ribosomal RNA is just as fundamental and widespread among bacteria as it
is in the animal kingdom. As a consequence, many antibiotics target
ribosomal RNA in bacteria. This rRNA is sufficiently unique that it can
be targeted without killing the infected organism, but also similar
enough among bacteria that individual antibiotics can kill many
different strains. Many of these antibiotics are naturally occurring
chemicals: products of the advantages bacteria can gain from killing
each other off independently!
f you have an Eclectus parrot, there's no doubt about the sex of your
pet--the bright red female can hardly be mistaken for a green male. No
guessing with budgies, either, as a mature male's cere, the area just
above the beak, is blue. And in the case of canaries, you can hear the
difference--only males sing. In some cases, though, you can't tell just
by looking--or listening!
Do you know what sex your bird is? While many caretakers are content to
guess, others want to know with certainty if their beloved Max is really
a Maxine. And if you're considering adding another bird to your
family's flock, knowing your pet's gender can help you choose the most
compatible cagemates.
When the gender of a bird can be determined visually, he or she is a
member of a DIMORPHIC species. All members of MONOMORPHIC species,
however, look the same, and you cannot distinguish males from females
based on their appearance. The latter group includes macaws, conures and
cockatoos. Some species of lovebirds are monomorphic, while others,
such as the Abyssinian, are dimorphic.
If your avian companion is monomorphic, however, your pet's identity
need not remain a mystery. Many avian caretakers choose to have their
birds surgically sexed. After anesthetizing the bird, a veterinarian
makes a small incision in the abdomen and is thus able to view the
animal's internal sex organs. This procedure is safe and quick when
executed by an experienced doctor, but is not recommended for very young
birds. As they have not yet reached sexual maturity, their sex organs
are much more difficult to distinguish.
Up until recent years, this invasive procedure was the only reliable
method available. Thanks to the advent of DNA sexing, however, birds can
be accurately sexed without the possible complications of surgery and
anesthesia. A blood sample is collected from a vein or toenail--a
procedure that can be done easily and painlessly by the bird's
caretaker--and sent via mail to a laboratory, where it is analyzed to
determine the bird's sex. Unlike surgical sexing, DNA sexing can be
accurately done on baby birds. Another advantage is that your pet will
not have to leave the comfort of his environment--and that's less stress
for both you and your feathered friend!
DNA sexing services are currently offered by a number of laboratories
worldwide. First on the scene was Zoogen Services located in Davis, CA.
Zoogen was founded in 1990, and to date has accurately sexed over
330,000 birds. In the beginning, the analysis process was somewhat
cumbersome, taking about a week to complete.
parrot dna
Only one drop of blood is needed to determine the sex of a parrot. The
blood is collected in a capillary tube which is like a tiny glass straw.
Enzymes (a protein that serves as a chemical catalysts that is released
at the end of the reaction, so it may be used again) in the blood,
start to break down the DNA (deoxyribonucleic acid - the genetic
material that all living things inherit from their parents) as soon as
the sample is taken. The sample is immediately placed in a preservative
solution. The Zoogen instructions tell you to use rubbing alcohol, 70-
ethanol, gin or vodka in case you lose the preservative provided by
them.
In my Biology II class, I ran DNA isolations on calf liver. Additives
such as .09- solution of Sodium Chloride (salt water) are used to
liberate proteins and to remove undissassociated nucleoproteins
(proteins associated with the nucleus where the DNA is found). I added
Sodium Dodecylsufate (SDS) which acts as a biological detergent to cut
through oil and to dissolve the membrane surrounding the nucleus so the
DNA could be retrieved.
At Zoogen, solutions are added to the sample. They are shaken and
centrifuged to separate the solution into several layers. Heavier
particles go to the bottom and lighter particles rise to the surface.
The DNA can be removed at this point and is a very thick, sticky small
mass. This step could take about a day to complete. More isolation
procedures are run to further dissolve the DNA which could take another
10 hours.
The isolated DNA is next dissolved in another solution containing
enzymes called restriction enzymes. In nature, these enzymes protect
against intruding DNA. They work to cut up foreign DNA restricting it
from surviving in your own cells. These enzymes recognize short
nucleotide (an organic unit consisting of a sugar molecule bonded to a
nitrogen base and a phosphate group - - nucleotides are the building
blocks of nucleic acids) sequences in DNA molecules and cut them at
specific points within the so-called recognition sequences. These pieces
of DNA are called restriction fragments. The differences in homologous
DNA sequences that result in restriction fragment lengths have been
dubbed restriction fragment length polymorphisms or RFLPs (pronounced
riflips). This procedure is used by thousands of labs over the last ten
years to examine DNA. It is a well-known tool of gene analysis and is
not experimental. Correctly done, DNA doesn't lie. I guess you can tell I
watched a lot of the Simpson Trial.
The DNA fragments are then placed near one end of a bed of gel that has
an electric current running through it. The DNA is negatively charged
and moves to the positive end of the gel. Smaller fragments move faster
than large ones. After about 18 hours, the fragments are arranged by
length. This procedure is called electrophoresis. When the DNA has been
run out (separated by length sizes) the gel is exposed to UV light. At
this point, the DNA can actually be seen (it glows because of the
chemicals added to it). The DNA (a double strand-stranded helical giant
molecule - it looks like a twisted ladder) can be "unzipped" or split
into two complementary strands. These splits are transferred to a nylon
membrane. The nylon membrane is immersed in a bath and a radioactive
probe. The probe is actually a stretch of DNA of a known sequence. The
species (breed) of the bird is necessary so they can use the correct
probe in identifying the sex of the bird. If you do not put the correct
species on, the test could be delayed or perhaps be incorrect. The
technicians can usually tell if you reported the wrong species, because
they can recognize most species' patterns. After having run over 90,000
samples, they have a lot of experience reading these results. The probe
seeks out the complimentary strands of DNA and bonds to it. They know
what the probe is and the places to which it will bond. Those places are
associated with pieces of DNA on the bird's sex chromosomes. The last
step is to expose x-ray film to the nylon membrane containing the
radioactive probe. Dark bands develop at the probe sites. The resulting
X-ray is a pattern which can be interpreted by technicians. The pattern
of these bands reveal the sex of your bird. Many animals, including
humans, have a pair of sex chromosomes, designated X and Y, that
determine an individuals sex. In humans, individuals with XY chromosomes
are male and XX chromosomes are female.
The sex of a human baby is determined by the father whether they get an X
or a Y. In contrast to this system, birds have sex chromosomes
designated Z and W. Males have ZZ and females are ZW. These are the
chromosomes used in the DNA sequence probe to determine the sex of a
bird. In birds, the female determines the sex of her offspring whether
they get Z or W chromosomes. Isn't science wonderful? Now you know how
DNA sex determination works. I think you really get a lot of technology
for your money.
Cloning, the copying of the same basically means anything . Genetikde , a
particular section of DNA , often used to create copies of a gene is
the method . DNA fragments generated in this way , is used in research .
with her husband in the DNA of an organism , the method used to create a
new life often called " somatic cell nucleus transfer "is called.
cloning in the biological sense , single-celled organisms is a form of
reproduction ( clonal growth ). Apart from these specific issues in
multicellular organisms, specialized cells that divide to form
themselves again, " Clonal reproduction is called . The best examples
are the human immune system cells . against a specific effect of these
cells to recognize pathogens , capable of producing the right antibodies
as cell clonal proliferation of war and disease are .
" Cloning " begins to be heard by the masses of the concept in 1997,
Scottish scientists at Roslin Institute , Dr . Wilmut and his team the
sheep " Dolly , " I began to produce . Part of the worldwide interest in
scientific development view , some of which are due to ethical problems
. In fact, much earlier than the foundation for cloning , based on
studies with bacteria .
based cloning can be divided into the three main headings :
* Recombinant DNA technology
* Çoğaltımsal cloning
* Therapeutic cloning Purpose
stored in DNA The genetic information , protein structure acts as an
intermediary in transferring a molecule Okoume . Copies can be solved by
DNA extracted molecules are localized . Messenger ribonucleic acid ,
called m - RNA , DNA from a specific carries the information of chemical
structures have been translated into polypeptide . m - RNA nucleotides,
and a single strand of DNA consists of patterns in the neck . On the
nucleotide sequence of the DNA helix is one of the matches . Polypeptide
molecules , DNA was separated from the m - RNA into ribosomes sticks ,
here are proteins produced in accordance with the incoming messages .
RNA molecules are combined in this way , just like a photo negative of
the positive and the co- inheritance case is the type of message across .
With these messages can be solved later in the cytoplasm, ribosomes and
amino acids through a combination of carrier will be used for RNA.
ribonukleotitlerinbirbirlerine RNAs are single-stranded nucleic acid
with the binding is occurring . DNA
When compared with molecular length is shorter. In almost all cells as
abundant
are present . DNA protein production to fulfill the function of a "call
molecules " to
is needed. This function is loaded ribonucleic acid sequence of
nucleotides settling corporate
Consisting of a single series ( such as DNA single strand of chain ) is a
high -quality molecules . DNA
molecules were found largely in the cell nucleus , are of RNAs into
cells have spread .
usually double- helix structure of DNA in the lane , while the single
şerittlidir RNA . However , DNA single -lane and double lane
RNA molecules are seen as well
Gene transferAn organism's cells , another organism's DNA is called to
the replacement of certain parts .
One of the applications of gene transfer is gene therapy . Today ,
however, many plants and animals through gene transfer is a new feature
win .
Dolly the sheep is the first that shows the importance of gene transfer .
Gene transfer can be achieved thanks to better health for future
generations .
DNA replication or DNA synthesis, the double- stranded DNA before cell
division is the process of copying . new DNA strands are copied almost
exactly the same , but from time to time due to errors in replication is
not a perfect copy (see mutation) , and the results of both the helix
consists of an old and a new thread . It is called semi- conservative
replication . DNA replication consists of three steps : initiation , two
recovery and termination
Recombinant DNA ..
Recombinant DNA or Recombinant DNA technologyOften obtained from
different biological species of DNA molecules , genetic engineering and
the cessation of DNA fragments obtained from different biological
processes and combining the results of this process produced the name
given to the new DNA molecules .
Recombinant DNA technology is used in many fields .
Recombinant DNA technology is used in many fields .
Genetic recombination events artificially realization is based on
recombinant DNA technology ( rDNA ), the first work in 1973 has started ,
and 80 in the giant steps forward , and today, the name most frequently
mentioned , and molecular genetic revolution has created a science has
become .
DNA, or deoxyribonucleic acid, is the hereditary material in humans and
almost all other organisms. Nearly every cell in a person’s body has the
same DNA. Most DNA is located in the cell nucleus (where it is called
nuclear DNA), but a small amount of DNA can also be found in the
mitochondria (where it is called mitochondrial DNA or mtDNA).
The information in DNA is stored as a code made up of four chemical
bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human
DNA consists of about 3 billion bases, and more than 99 percent of those
bases are the same in all people. The order, or sequence, of these
bases determines the information available for building and maintaining
an organism, similar to the way in which letters of the alphabet appear
in a certain order to form words and sentences.
DNA bases pair up with each other, A with T and C with G, to form units
called base pairs. Each base is also attached to a sugar molecule and a
phosphate molecule. Together, a base, sugar, and phosphate are called a
nucleotide. Nucleotides are arranged in two long strands that form a
spiral called a double helix. The structure of the double helix is
somewhat like a ladder, with the base pairs forming the ladder’s rungs
and the sugar and phosphate molecules forming the vertical sidepieces of
the ladder.
An important property of DNA is that it can replicate, or make copies of
itself. Each strand of DNA in the double helix can serve as a pattern
for duplicating the sequence of bases. This is critical when cells
divide because each new cell needs to have an exact copy of the DNA
present in the old cell.
Keratinocyte cancers
These are by far the most common skin cancers. They are called keratinocyte carcinomas or keratinocyte cancers because
when seen under a microscope, their cells look like early forms of
keratinocytes, the most common type of skin cell. Most keratinocyte
cancers are basal cell carcinomas or squamous cell carcinomas.
Basal cell carcinoma
This is not only the most common type of
skin cancer, but the most common type of cancer in humans. About 8 out
of 10 skin cancers are basal cell carcinomas (also called basal cell cancers). When seen under a microscope, the cells in these cancers look like cells in the lowest layer of the epidermis, called the basal cell layer.
These cancers usually develop on sun-exposed
areas, especially the head and neck. Basal cell carcinoma was once
found almost entirely in middle-aged or older people. Now it is also
being seen in younger people, probably because they are spending more
time in the sun.
These cancers tend to grow slowly. It’s very
rare for a basal cell cancer to spread to other parts of the body. But
if a basal cell cancer is left untreated, it can grow into nearby areas
and invade the bone or other tissues beneath the skin.
After treatment, basal cell carcinoma can
recur (come back) in the same place on the skin. People who have had
basal cell cancers are also more likely to get new ones elsewhere on the
skin. As many as half of the people who are diagnosed with one basal
cell cancer will develop a new skin cancer within 5 years.
Squamous cell carcinoma
About 2 out of 10 skin cancers are squamous cell carcinomas (also called squamous cell cancers). The cells in these cancers look like abnormal versions of the squamous cells seen in the outer layers of the skin.
These cancers commonly appear on sun-exposed
areas of the body such as the face, ears, neck, lips, and backs of the
hands. They can also develop in scars or chronic skin sores elsewhere.
They sometimes start in actinic keratoses (described below). Less often,
they form in the skin of the genital area.
Squamous cell cancers are more likely to
grow into deeper layers of skin and spread to other parts of the body
than basal cell cancers, although this is still uncommon.
Keratoacanthomas are dome-shaped
tumors that are found on sun-exposed skin. They may start out growing
quickly, but their growth usually slows down. Many keratoacanthomas
shrink or even go away on their own over time without any treatment. But
some continue to grow, and a few may even spread to other parts of the
body. Their growth is often hard to predict, so many skin cancer experts
consider them a type of squamous cell skin cancer and treat them as
such.
What Are mRNA, rRNA and tRNA?
What Are mRNA, rRNA and tRNA?
RNA is a critical component of every single living cell in the universe. Without it, life as we know it could not exist. There are three types of RNA, each with a unique function. mRNA is used to produce proteins from genes. rRNA, along with protein, forms the ribosome, which translates mRNA. tRNA is the link between the two other types of RNA.
RNA Features
1. RNA, or ribonucleic acid, is a linear polymer of adenine, thymine, cytosine, and uracil that is created in the cell by a process called transcription, and it differs from DNA in several ways. First, the ribose sugars on DNA nucleotides are short one hydroxyl group compared to RNA, hence the name deoxyribonucleic acid. This key modification makes RNA much more chemically reactive. Second, DNA uses thymine to base pair with cytosine, while RNA uses uracil. Third, DNA tends to form into a helix of double-stranded nucleotides, with base pairs making up the "rungs" of the helical ladder. RNA can be found in single-stranded form, but it more commonly forms complex three-dimensional structures, and this feature usually serves to confer functionality on RNA molecules.
RNA Synthesis
2. RNA transcription is a process mediated by RNA polymerase, an enzyme that creates an RNA complement to template DNA with the help of a complex of proteins. Transcription is heavily regulated by promoter elements and inhibitors. All three types of RNA are synthesized in this manner.
mRNA
3. mRNA, or messenger RNA, is the link between a gene and a protein. The gene is transcribed by RNA polymerase, and the resulting mRNA travels to the cytoplasm, where it is translated by ribosomes into a protein with the help of tRNA. This form of RNA is extensively altered post-transcriptionally with modifications such as methylguanosine caps and polyadenosine tails. Eukaryotic mRNA frequently includes introns which must be spliced out of the message to form the mature mRNA molecule.
rRNA
4. rRNA, or ribosomal RNA, is a major component of ribosomes. After transcription, these RNA molecules travel to the cytoplasm and join with other rRNAs and many proteins to form a ribosome. rRNA is used both for structural and functional purposes. Many reactions in the translational process are catalyzed by key portions of certain rRNAs in the ribosome.
tRNA
5. tRNA, or transfer RNA, is the "decoder" of the mRNA message during protein translation. After transcription, tRNA is extensively modified to include nonstandard bases such as pseudouridine, inosine, and methylguanosine. By themselves, ribosomes cannot form a protein when the mRNA makes contact. The anticodon, a string of three key bases on the tRNA, match with three bases on the mRNA message called the codon. That is only the first function of tRNA, as each molecule also carries with it an amino acid which matches the mRNA codon. The ribosome functions to polymerize the amino acids linked to the tRNA into a functional protein
RNA is a critical component of every single living cell in the universe. Without it, life as we know it could not exist. There are three types of RNA, each with a unique function. mRNA is used to produce proteins from genes. rRNA, along with protein, forms the ribosome, which translates mRNA. tRNA is the link between the two other types of RNA.
RNA Features
1. RNA, or ribonucleic acid, is a linear polymer of adenine, thymine, cytosine, and uracil that is created in the cell by a process called transcription, and it differs from DNA in several ways. First, the ribose sugars on DNA nucleotides are short one hydroxyl group compared to RNA, hence the name deoxyribonucleic acid. This key modification makes RNA much more chemically reactive. Second, DNA uses thymine to base pair with cytosine, while RNA uses uracil. Third, DNA tends to form into a helix of double-stranded nucleotides, with base pairs making up the "rungs" of the helical ladder. RNA can be found in single-stranded form, but it more commonly forms complex three-dimensional structures, and this feature usually serves to confer functionality on RNA molecules.
RNA Synthesis
2. RNA transcription is a process mediated by RNA polymerase, an enzyme that creates an RNA complement to template DNA with the help of a complex of proteins. Transcription is heavily regulated by promoter elements and inhibitors. All three types of RNA are synthesized in this manner.
mRNA
3. mRNA, or messenger RNA, is the link between a gene and a protein. The gene is transcribed by RNA polymerase, and the resulting mRNA travels to the cytoplasm, where it is translated by ribosomes into a protein with the help of tRNA. This form of RNA is extensively altered post-transcriptionally with modifications such as methylguanosine caps and polyadenosine tails. Eukaryotic mRNA frequently includes introns which must be spliced out of the message to form the mature mRNA molecule.
rRNA
4. rRNA, or ribosomal RNA, is a major component of ribosomes. After transcription, these RNA molecules travel to the cytoplasm and join with other rRNAs and many proteins to form a ribosome. rRNA is used both for structural and functional purposes. Many reactions in the translational process are catalyzed by key portions of certain rRNAs in the ribosome.
tRNA
5. tRNA, or transfer RNA, is the "decoder" of the mRNA message during protein translation. After transcription, tRNA is extensively modified to include nonstandard bases such as pseudouridine, inosine, and methylguanosine. By themselves, ribosomes cannot form a protein when the mRNA makes contact. The anticodon, a string of three key bases on the tRNA, match with three bases on the mRNA message called the codon. That is only the first function of tRNA, as each molecule also carries with it an amino acid which matches the mRNA codon. The ribosome functions to polymerize the amino acids linked to the tRNA into a functional protein
The Role of mRNA in Translation
DNA (deoxyribonucleic acid) contains the genetic information to
synthesize all the proteins in the cell. However, DNA in the nucleus is
separated from the ribosomes in the cytoplasm where protein synthesis
occurs. RNA (ribonucleic acid) serves as an intermediary between the DNA
in the nucleus and the end protein. Three types of RNA are involved in
the process: messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA
(tRNA).
Transcription
1. Genes in the DNA are transcribed into mRNA. Eukaryotes modify the initial mRNA (pre-mRNA) sequence by removing introns (sections of DNA transcribed but not used in the final protein). The mRNA then travels to ribosomes.
Translation
2. Translation uses the code on the mRNA to synthesize a protein. Translation occurs in three stages: initiation, elongation, and termination.
Initiation
3. The small subunit of the ribosome binds to the mRNA. When a start codon (a codon is a sequence of bases that code for an amino acid) is detected on the mRNA, the large subunit of the ribosome attaches to the small subunit and matches an initiator tRNA to the codon.
Elongation
4. During elongation, the ribosome continues to match codons on the mRNA with tRNA carrying the corresponding amino acid. Each amino acid is linked to the subsequent amino acid by a peptide bond.
Termination
5. When a stop codon is reached on the mRNA, the protein is released from the ribosome, and the large and small subunits of the ribosome detach from each other.
Transcription
1. Genes in the DNA are transcribed into mRNA. Eukaryotes modify the initial mRNA (pre-mRNA) sequence by removing introns (sections of DNA transcribed but not used in the final protein). The mRNA then travels to ribosomes.
Translation
2. Translation uses the code on the mRNA to synthesize a protein. Translation occurs in three stages: initiation, elongation, and termination.
Initiation
3. The small subunit of the ribosome binds to the mRNA. When a start codon (a codon is a sequence of bases that code for an amino acid) is detected on the mRNA, the large subunit of the ribosome attaches to the small subunit and matches an initiator tRNA to the codon.
Elongation
4. During elongation, the ribosome continues to match codons on the mRNA with tRNA carrying the corresponding amino acid. Each amino acid is linked to the subsequent amino acid by a peptide bond.
Termination
5. When a stop codon is reached on the mRNA, the protein is released from the ribosome, and the large and small subunits of the ribosome detach from each other.
RNA – mRNA
RNA – mRNA
RNA is always single stranded. It contains mostly the bases adenine, guanine, cytosine and uracil. There are few unusual substituted bases. Although there is a certain amount of random coiling in extracted mRNA, there is no base pairing. In fact base pairing in the mRNA strand destroys its biological activity.
Since mRNA is transcribed on DNA (genes), its base sequence is complementary to that of the segment of DNA on which it is transcribed. This has been demonstrated by hybridization experiments in which artificial RNADNA double strands are produced. Hydrization takes place only if the DNA and RNA strands are complementary.
Usually each gene transcribes its own mRNA. Therefore, there are approximately as many types of mRNA molecules as there are genes. There may be 1,000 to 10.000 different species of mRNA in a cell. These mRNA types differ only in the sequence of their bases and in length.
When one gene (cistron) codes for a single mRNA strand the mRNA is said to be monocistronic. In many cases, however, several adjacent cistrons may transcribe an mRNA molecule, which is then said to be polycistronic or polygenic.
The mRNA molecule has the following structural features:
1. Cap. At the 5′ end of the mRNA molecule in most eukaryote cells and animal virus molecules is found a ‘cap’. This is blocked methylated structure, m7Gpp Nmp Np or m7Gpp Nmp Nmp Np. where: N = any of the four nucleotides and Nmp = 20 methyl ribose. The rate of protein synthesis depends upon the presence of the cap. Without the cap mRNA molecules bind very poorly to the ribosomes.
2. Noncoding region 1 (NC1). The cap is followed by a region of 10 to 100 nucleotides. This region is rich in A and U residues, and does not translate protein.
3. The initiation codon is A UG in both prokaryotes and eukaryotes.
4. The coding region consists of about 1,500 nucleotides on the average and translates protein
RNA is always single stranded. It contains mostly the bases adenine, guanine, cytosine and uracil. There are few unusual substituted bases. Although there is a certain amount of random coiling in extracted mRNA, there is no base pairing. In fact base pairing in the mRNA strand destroys its biological activity.
Since mRNA is transcribed on DNA (genes), its base sequence is complementary to that of the segment of DNA on which it is transcribed. This has been demonstrated by hybridization experiments in which artificial RNADNA double strands are produced. Hydrization takes place only if the DNA and RNA strands are complementary.
Usually each gene transcribes its own mRNA. Therefore, there are approximately as many types of mRNA molecules as there are genes. There may be 1,000 to 10.000 different species of mRNA in a cell. These mRNA types differ only in the sequence of their bases and in length.
When one gene (cistron) codes for a single mRNA strand the mRNA is said to be monocistronic. In many cases, however, several adjacent cistrons may transcribe an mRNA molecule, which is then said to be polycistronic or polygenic.
The mRNA molecule has the following structural features:
1. Cap. At the 5′ end of the mRNA molecule in most eukaryote cells and animal virus molecules is found a ‘cap’. This is blocked methylated structure, m7Gpp Nmp Np or m7Gpp Nmp Nmp Np. where: N = any of the four nucleotides and Nmp = 20 methyl ribose. The rate of protein synthesis depends upon the presence of the cap. Without the cap mRNA molecules bind very poorly to the ribosomes.
2. Noncoding region 1 (NC1). The cap is followed by a region of 10 to 100 nucleotides. This region is rich in A and U residues, and does not translate protein.
3. The initiation codon is A UG in both prokaryotes and eukaryotes.
4. The coding region consists of about 1,500 nucleotides on the average and translates protein
MRNA From a Cell
MRNA From a Cell
A cell's genetic blueprint is encoded within its genetic material, or DNA. As the DNA never leaves the nucleus of the cell, in order for this information to get into the cytoplasm where other proteins and biochemical components reside, it is necessary to first transcribe the DNA into messenger RNA (mRNA or poly(A) RNA). This mRNA then becomes translated into proteins that carry out many functions of the cell. To detect or quantify very rare mRNAs, make probes for microarrays or construct libraries of complementary DNA molecules, mRNA must be isolated. However, total RNA (i.e. all the RNA in a cell) extraction and subsequent mRNA isolation are not mutually exclusive processes; the former must be performed in order for mRNA to be extracted.
Isolation of mRNA From Total RNA ..
TRIzol homogenization:
Total RNA includes all mRNA , transfer RNA, ribosomal RNA, and other noncoding RNAs. To separate these from other cellular components, the cell is first burst open to release its contents. This is done by resuspending cells pelleted by centrifuging (spinning at high speeds) in TRIzol Reagent (Life Technologies). Other versions of TRIzol (such as Ambion's TRI Reagent) work similarly.
Total RNA Isolation:
A series of centrifugations is used to separate the different components (proteins, DNA, RNA) of the cell into layers, or phases, within the suspension. The top, yellow-colored phase is composed of fat and can be discarded. The desired phase is tinted red, contains the total RNA and is retained. After performing a phenol-chloroform extraction and a series of alcohol washes using isopropanol and ethanol, the RNA can be pelleted for mRNA isolation. Add RNase inhibitors to prevent this enzyme from degrading the total RNA.
mRNA Extraction:
It is common to use a kit to isolate mRNAs, as homemade lab protocols do not generate large quantities of highly purified mRNAs. Commercial kits include Invitrogen's FastTrack 2.0 or Ambion's Poly(A)Pure mRNA Isolation Kit. These basic steps are common to such kits:
a) Mix the RNase-inhibited lysis buffer provided in the kit with up to 300 microliters of total RNA.
b) Heat for 5 minutes at 65 degrees Celsius and then immediately cool the sample on ice for one minute.
c) Mix this with 0.5M Sodium Chloride and then completely dissolve Oligo dT (oligodeoxythymidylic acid) in this sample.
d) Centrifuge this sample and recover the supernatant, which is washed several times in a series of binding and low salt buffers provided in the kits.
e) Elute mRNA several times until a kit-specified volume (e.g. 500 microliters) is obtained.
f) Precipitate the eluate by sodium acetate and ethanol precipitation. Re-suspend in up to 20 microliters of diethylpyrocarbonate (DEPC)-treated water.
g) Store at -80 degrees Celsius and check for quality and quantity by spectrophotometry.
A cell's genetic blueprint is encoded within its genetic material, or DNA. As the DNA never leaves the nucleus of the cell, in order for this information to get into the cytoplasm where other proteins and biochemical components reside, it is necessary to first transcribe the DNA into messenger RNA (mRNA or poly(A) RNA). This mRNA then becomes translated into proteins that carry out many functions of the cell. To detect or quantify very rare mRNAs, make probes for microarrays or construct libraries of complementary DNA molecules, mRNA must be isolated. However, total RNA (i.e. all the RNA in a cell) extraction and subsequent mRNA isolation are not mutually exclusive processes; the former must be performed in order for mRNA to be extracted.
Isolation of mRNA From Total RNA ..
TRIzol homogenization:
Total RNA includes all mRNA , transfer RNA, ribosomal RNA, and other noncoding RNAs. To separate these from other cellular components, the cell is first burst open to release its contents. This is done by resuspending cells pelleted by centrifuging (spinning at high speeds) in TRIzol Reagent (Life Technologies). Other versions of TRIzol (such as Ambion's TRI Reagent) work similarly.
Total RNA Isolation:
A series of centrifugations is used to separate the different components (proteins, DNA, RNA) of the cell into layers, or phases, within the suspension. The top, yellow-colored phase is composed of fat and can be discarded. The desired phase is tinted red, contains the total RNA and is retained. After performing a phenol-chloroform extraction and a series of alcohol washes using isopropanol and ethanol, the RNA can be pelleted for mRNA isolation. Add RNase inhibitors to prevent this enzyme from degrading the total RNA.
mRNA Extraction:
It is common to use a kit to isolate mRNAs, as homemade lab protocols do not generate large quantities of highly purified mRNAs. Commercial kits include Invitrogen's FastTrack 2.0 or Ambion's Poly(A)Pure mRNA Isolation Kit. These basic steps are common to such kits:
a) Mix the RNase-inhibited lysis buffer provided in the kit with up to 300 microliters of total RNA.
b) Heat for 5 minutes at 65 degrees Celsius and then immediately cool the sample on ice for one minute.
c) Mix this with 0.5M Sodium Chloride and then completely dissolve Oligo dT (oligodeoxythymidylic acid) in this sample.
d) Centrifuge this sample and recover the supernatant, which is washed several times in a series of binding and low salt buffers provided in the kits.
e) Elute mRNA several times until a kit-specified volume (e.g. 500 microliters) is obtained.
f) Precipitate the eluate by sodium acetate and ethanol precipitation. Re-suspend in up to 20 microliters of diethylpyrocarbonate (DEPC)-treated water.
g) Store at -80 degrees Celsius and check for quality and quantity by spectrophotometry.
Why is there a controversy about using embryonic stem cells?
Embryonic stem cells are obtained from early-stage embryos — a group of
cells that forms when a woman's egg is fertilized with a man's sperm in
an in vitro fertilization clinic. Because human embryonic stem cells
are extracted from human embryos, several questions and issues have been
raised about the ethics of embryonic stem cell research.
The National Institutes of Health created guidelines for human stem cell
research in 2009. Guidelines included defining embryonic stem cells and
how they may be used in research and donation guidelines for embryonic
stem cells. Also, guidelines stated embryonic stem cells may only be
used from embryos created by in vitro fertilization when the embryo is
no longer needed.
Where do these embryos come from?
The embryos being used in embryonic stem cell research come from eggs
that were fertilized at in vitro fertilization clinics but never
implanted in a woman's uterus. The stem cells are donated with informed
consent from donors. The stem cells can live and grow in special
solutions in test tubes or petri dishes in laboratories.
Why can't researchers use adult stem cells instead?
Although research into adult stem cells is promising, adult stem cells
may not be as versatile and durable as are embryonic stem cells. Adult
stem cells may not be able to be manipulated to produce all cell types,
which limits how adult stem cells can be used to treat diseases.
Adult stem cells also are more likely to contain abnormalities due to
environmental hazards, such as toxins, or from errors acquired by the
cells during replication. However, researchers have found that adult
stem cells are more adaptable than was initially suspected.
Where do stem cells come from?
Researchers have discovered several sources of stem cells:
Embryonic stem cells. These stem cells come from embryos that are
three to five days old. At this stage, an embryo is called a blastocyst
and has about 150 cells.
These are pluripotent (ploo-RIP-uh-tunt) stem cells, meaning they
can divide into more stem cells or can become any type of cell in the
body. This versatility allows embryonic stem cells to be used to
regenerate or repair diseased tissue and organs, although their use in
people has been to date limited to eye-related disorders such as macular
degeneration.
Adult stem cells. These stem cells are found in small numbers in
most adult tissues, such as bone marrow or fat. Compared with embryonic
stem cells, adult stem cells have a more limited ability to give rise to
various cells of the body.
Until recently, researchers thought adult stem cells could create
only similar types of cells. For instance, researchers thought that stem
cells residing in the bone marrow could give rise only to blood cells.
However, emerging evidence suggests that adult stem cells may be
able to create unrelated types of cells. For instance, bone marrow stem
cells may be able to create bone or heart muscle cells. This research
has led to early-stage clinical trials to test usefulness and safety in
people. For example, adult stem cells are currently being tested in
people with neurological or heart disease.
Adult cells altered to have properties of embryonic stem cells
(induced pluripotent stem cells). Scientists have successfully
transformed regular adult cells into stem cells using genetic
reprogramming. By altering the genes in the adult cells, researchers can
reprogram the cells to act similarly to embryonic stem cells.
This new technique may allow researchers to use these reprogrammed
cells instead of embryonic stem cells and prevent immune system
rejection of the new stem cells. However, scientists don't yet know if
altering adult cells will cause adverse effects in humans.
Researchers have been able to take regular connective tissue cells
and reprogram them to become functional heart cells. In studies, animals
with heart failure that were injected with new heart cells experienced
improved heart function and survival time.
Perinatal stem cells. Researchers have discovered stem cells in
amniotic fluid in addition to umbilical cord blood stem cells. These
stem cells also have the ability to change into specialized cells.
Amniotic fluid fills the sac that surrounds and protects a
developing fetus in the uterus. Researchers have identified stem cells
in samples of amniotic fluid drawn from pregnant women during a
procedure called amniocentesis, a test conducted to test for
abnormalities.
More study of amniotic fluid stem cells is needed to understand
their potential.
Why are stem cells important?
Stem cells represent an exciting area in medicine because of their
potential to regenerate and repair damaged tissue. Some current
therapies, such as bone marrow transplantation, already make use of stem
cells and their potential for regeneration of damaged tissues. Other
therapies are under investigation that involves transplanting stem cells
into a damaged body part and directing them to grow and differentiate
into healthy tissue.
What are the different types of stem cells?
Embryonic stem cells
During the early stages of embryonic development the cells remain
relatively undifferentiated (immature) and appear to possess the ability
to become, or differentiate, into almost any tissue within the body.
For example, cells taken from one section of an embryo that might have
become part of the eye can be transferred into another section of the
embryo and could develop into blood, muscle, nerve, or liver cells.
Cells in the early embryonic stage are totipotent (see above) and can
differentiate to become any type of body cell. After about seven days,
the zygote forms a structure known as a blastocyst, which contains a
mass of cells that eventually become the fetus, as well as trophoblastic
tissue that eventually becomes the placenta. If cells are taken from
the blastocyst at this stage, they are known as pluripotent, meaning
that they have the capacity to become many different types of human
cell. Cells at this stage are often referred to as blastocyst embryonic
stem cells. When any type of embryonic stem cells is grown in culture in
the laboratory, they can divide and grow indefinitely. These cells are
then known as embryonic stem cell lines.
replication of dna
DNA replication, DNA replication or DNA synthesis, cell division Prior
to double-stranded DNA'S copy the process of. Copied new DNA strands are
almost entirely the same, but from time to time due to copying errors
çoğalmadaki excellent not (see mutation), and resulting in both an old
and a spiral new made from yarn. This semi-conservative replication is
called. DNA replication process consists of three phases: initiation,
replication and
termination
Initiation
Starting several factors alamasında replication center'What is
collected. DNA replication in the center opens, the drop-down yarns are
partially a "replication bubble" form, a replication at both ends fork
found. Each enzyme group center runs away and moves to open the DNA
strands new yarn synthesis. Enzymes involved in this stage,
collectively, the "pre-replication complex is called. They are:
Helicase: DNA leads.Primaz: Required for DNA replication RNA "Primer"
strands synthesis. DNA haloenzim: The real growth in process a
collection of enzymes that perform
The proliferation of DNA polymerase process When it comes to the end
operation parallel Due to the lack of another problem arises: yarn trim
the 5 'end of the RNA primer strand connect to not enough space, so that
the DNA polymerase Connect The end of the copy, it will be impossible.
Solution of the problem in bacteria (or prokaryoticLarda) is very
easy: The circular structure of DNA in these organisms, so that the DNA
of a "tip" there. More complex eukaryoticLarda this "clever" is solved.
Telomere Every living thing is fixed according to the syntax of the ends
of DNA, called nucleotides (human 5 'GGGTTA 3') and in this short
sequence is repeated thousands of times. Also telomerase enzyme along
with the name corresponding to the telomere repeat sequence is a short
strand of RNA primer. Telomerase DNA replication process telomere at the
end of Connect carried on their own using the primer strand extends
telomeres. Thus, telomere RNA lining Connect copy, it is possible, but
the telomerase gene to prolong the long strands of DNA strand opposite
the other remains. This is a long remaining "single strand" in some
proteins help bent DNA end in itself creates a small ring. Ring become
not exposed to enzymes break down due to receipt of single-stranded DNA
molecules. The final stage of the copying errors that may have occurred
during the synthesis of DNA is determined by reading some enzimlerce, if
you have copied the wrong nuclease defective parts enzyme called DNA
breaks, DNA polymerase then fills in the gaps.
Figure 101: DNA helix stabilization to prevent the arms from each other
leaving again dolanmalarını enzymes (HSE) fixed amounts of both arms. In
the center, showing a separation of the DNA arms.
Figure 102: After leaving the two DNA polymerase enzymes that are
missing in both halves of the arm, complete with materials present
environment.
As is known, the cells divide and multiply. So what happens to DNA as a
result of this division? There is a single chain of DNA in the cell.
However, the newly formed cell will also need a DNA. To resolve this
deficit every stage of the process occurs in a separate a series of
miracle. As a result, a copy of the DNA of the cell division shortly
before the new cell is created and transferred.
DNA to replicate itself is divided into two parts, before the mutual.
This event takes place is quite an interesting way. Structure of the
middle of the DNA molecule resembles a spiral staircase, by an enzyme
called DNA helicase, is divided into two like a zipper. Stabilization of
the helix of DNA enzymes to prevent the arms from each other leaving
again dolanmalarını fixed amounts of both arms. (Figure 101)
Now divided into two halves of DNA. Both halves of the part that is
missing in (equivalents) present in the materials is completed.
Shortcomings in the completion work is carried out by DNA polymerase.
Thus, the two new DNA molecules are produced. (Figure 102)
Match several times during the emergence of new DNA molecules are
controlled by the controller enzymes. If you have made a mistake-that
these errors are detected and corrected immediately-may be crucial.
Correct password instead kopartılıp actually brought and mounted. All
these operations are made so that at a dizzying pace, while generating
up to 3,000 digits of nucleotide enzymes in charge of all these steps
and should be checked several times by the corrections made. (Figure
103)
Produced new DNA molecule, as a result of external influences can be
made more errors than normal. This time, the cell ribosomes, DNA, DNA
repair enzymes begin to produce in accordance with the orders. Thus, the
DNA will be protected and shall ensure the continuation of the lineage.
(Figure 104)
Here is the whole day, you never know when your life to continue without
any problems in your body admirable thoroughness and responsibility
made in the understanding of the numerous procedures and controls,
measures are taken. Everyone is completely and successfully fulfill the
task. Here is the smallest number of atoms and molecules of the Almighty
Allah, the greatest of our lives and the beautiful healthy In order to
maintain a service, has given way.
Biriyse most admirable aspects of this topic, as well as the structure
of DNA that controls both the production of these enzymes, according to
the information stored in DNA and proteins, DNA is made of the orders
and control. In the center there is intertwined so great that a system,
consisting of such a system gradually becomes in any way, this is not
possible by chance. Because the enzyme is DNA to the DNA of the enzyme
to be, that is for both of the cell, membrane, there must be complete
until all the other complex organelles.
Succession of organisms so-called "useful coincidences" as a result of
"gradual" claiming to have developed the theory of evolution, as in many
aspects than the above-mentioned before that we have DNA or enzymes
that are now in the face of unanswered questions. DNA and the enzyme are
required to have at the same time, which put forward the theory of
evolution is an impossible dream of the realization of mechanisms.
Chromosomes and DNA
Chromosomes are DNA wrapped around proteins to form an X-shaped
structure. The diagram will help you see the relationship. 1.
Chromosomes are found in the nucleus 2. Chromosomes are made of DNA 3.
Sections of chromosomes are called genes DNA - deoxyribonucleic acid (it
is the genetic code that contains all the information needed to build
and maintain an organism) Each organism has a distinct number of
chromosomes, in humans, every cell contains 46 chromosomes. Other
organisms have different numbers, for instance, a dog has 78 chromosomes
per cell. Somatic Cells - body cells, such as muscle, skin, blood
...etc. These cells contain a complete set of chromosomes (46 in humans)
and are called DIPLOID. Sex Cells - also known as gametes. These cells
contain half the number of chromosomes as body cells and are called
HAPLOID Chromosomes come in pairs, called Homologous Pairs (or
homologs). Imagine homologs as a matching set, but they are not exacly
alike, like a pair of shoes. Diploid cells have 23 homologous pairs =
total of 46 Haploid cells have 23 chromosomes (that are not paired) =
total of 23 Sex Determination Chromosomes determine the sex of an
offspring. In humans, a pair of chromosomes called SEX CHROMOSOMES
determine the sex. If you have XX sex chromosomes - you are female If
you have XY sex chromosomes - you are male During fertilization, sperm
cells will either contain an X or a Y chromosome (in addition to 22
other chromosomes - total of 23). If a sperm containing an X chromosome
fertilizes an egg, the offspring will be female. If a sperm cell
containing a Y chromosome fertilizes an egg, the offspring will be male.
Creation of a Zygote When two sex cells, or gametes come together, the
resulting fertilized egg is called a ZYGOTE Zygotes are diploid and have
the total 46 chromosomes (in humans) Karyotype A karyotype is a picture
of a person's (or fetus) chromosomes. A karyotype is often done to
determine if the offspring has the correct number of chromosomes. An
incorrect number of chromosomes indicates that the child will have a
condition, like Down Syndrome Notice that a person with Down Syndrome
has an extra chromosome #21. Instead of a pair, this person has 3
chromosomes - a condition called TRISOMY (tri = three) Trisomy results
when chromosomes fail to separate - NONDISJUNCTION - when sex cells are
created. The resulting egg or sperm has 24 instead of the normal 23.
Other conditions result from having the wrong number of chromosomes:
Klinefelters Syndrome - XXY (sex chromosomes) Edward Syndrome - Trisomy
of chromosome
ribonucleic acid
A biologically important molecule, ribonucleic acid (RNA) is similar in
some respects to deoxyribonucleic acid (DNA) but has some important
structural and functional differences. There are several types of
ribonucleic acid, each of which plays a different role within the cell.
Ribonucleic acids perform several essential tasks in protein synthesis
and are involved in gene regulation.
RNA and DNA are both called nucleic acids and share a similar basic
structure. Both types of nucleic acid are made up of units called
nucleotides. Each nucleotide is composed of three molecules: a
phosphate, a sugar and a nitrogenous base. There are several different
nitrogenous bases, and it is the sequence of these molecules that allows
DNA and RNA to store and transmit information about the long-term and
day-to-day maintenance of the cell.
Although they share some similarities, ribonucleic acid and
deoxyribonucleic acid molecules are different in three important ways.
First, an RNA molecule is single-stranded, whereas DNA is a
double-stranded molecule. Second, RNA contains a sugar called ribose,
and DNA contains a sugar called deoxyribose. The third difference is
that in DNA, the complementary base pair for adenine is thymine; whereas
in RNA, the base pair for adenine is a modified version of thymine
known as uracil.
There are three main types of ribonucleic acid. These are transfer RNA
(tRNA), messenger RNA (mRNA) and ribosomal RNA (rRNA). These three
molecules are structurally similar but perform very different functions.
Messenger RNA is the product of a process called transcription. In this
process, the genetic code carried in a section of DNA is copied,
resulting in the synthesis of a molecule of mRNA. The mRNA is an exact
copy of a section of DNA that codes for a single protein. After it has
been made, this mRNA travels from the cell's nucleus to the cytoplasm,
where it undergoes a new cellular process with help from another type of
ribonucleic acid.
In the cytoplasm of the cell, the mRNA comes into contact with transfer
RNA molecules. Transfer RNA helps manufacture proteins by transporting
amino acids to the site of protein synthesis. The tRNA uses mRNA
molecules as a template for building the protein by “reading” the mRNA
molecule to determine the order in which amino acids are placed in the
protein chain. This process is called translation.
The third type of RNA, ribosomal RNA, is the site at which translation
occurs. Ribosomal RNA molecules are the site at which mRNA is translated
into proteins. Ribosomal RNA helps in this process by interacting with
both messenger and transfer RNA molecules and by acting as a site of
enzyme activity.
Other types of ribonucleic acid include micro RNA and double-stranded
RNA. Micro RNA is used by cells to help regulate the transcription of
messenger RNA, and can both increase or decrease the rate at which a
particular gene is made into proteins. Double-stranded RNA, which is
found in certain types of viruses, can enter cells and interfere with
translation and transcription processes by acting in a manner similar to
micro RNA.
Genetic Basics
It’s in your genes. That’s how scientists explain the physical
characteristics, personality traits, and behaviors which make each human
unique. The clues carried in our genes -- in the form of DNA --are now
used to determine criminal guilt or innocence, resolve paternity or
maternity questions, predict the chance of inheriting a disease or
medical condition, and even trace the long-distant ancestors of the
human family tree.
Your body is made up of tiny units called cells – as many as 100
trillion of them, according to some estimates. Within the nucleus of
every one of these cells is a set of instructions which tell the cell
what role it will play in your body. These instructions, essentially a
blueprint or recipe for building different parts of the cell, come in
the form of a molecule called DNA. Short for deoxyribonucleic acid, DNA
consists of two thread-like strands that are linked together in the
shape of a double helix.
What is DNA?
DNA is made up of four chemical bases: Adenine (A), Cytosine (C),
Thymine (T), and Guanine (G). These bases are combined into pairs –
adenine with thymine and cytosine with guanine – to make up the “rungs”
of the DNA ladder (see Figure 21.1). Each “rung,” more accurately called
a base pair, is one of three billion such pairs which work together to
provide the instructions for building and maintaining a human being –
the human genome. The exact order in which these base pairs are combined
is called the DNA sequence. Much in the way letters of the alphabet are
combined to form words and sentences, the sequence of these bases are
the “letters” which spell out the genetic code.
What is a Chromosome?
Within the nucleus of each cell, the DNA molecules are coiled around
proteins into tiny structures called chromosomes. In humans, each cell
normally contains 23 pairs of chromosomes, for a total of 46. One
chromosome in each pair is inherited from the mother, and the other from
the father. Twenty-two of these pairs, sometimes called autosomes, look
the same in both males and females. The 23rd pair, called the sex
chromosome because it determines gender, is the one which differentiates
males and females. Females have two copies of the X chromosome, one
from each parent, while males have one X chromosome from their mother,
and one Y chromosome from their father. It is the father who determines
the sex of his child.
What is a Gene?
Genes are sections or segments of DNA that form the individual units of
heredity. They are carried on the chromosomes and contain instructions
for making molecules called proteins. Each protein enables a cell to
perform its own special function. The hemoglobin in red blood cells, for
example, is responsible for transporting oxygen throughout your body.
Another protein, insulin, helps you metabolize your food. The keratin
protein is what helps your hair and nails to grow. If you look at DNA as
a recipe for creating a living thing, then genes and proteins are the
ingredients which work together to build, repair, and run your body.
The traits which make us each unique are also inherited from our
ancestors. Physical characteristics such as curly hair, blue eyes, and a
tendency for acne are all determined by our genes. Scientists also
believe that many emotional and behavioral traits, at least in part, are
influenced by an individual’s genetic makeup. Eating habits,
intelligence, a penchant for aggressiveness, and even sleeping patterns
all have their roots in our DNA.
Because genes are carried on the chromosomes, humans have two copies of
each gene, one inherited from the mother and one from the father. The
two copies aren’t necessarily the same, however. Just like snowflakes,
genes come in variant forms. These variations are known as alleles.
Different alleles are what produce variations in inherited traits. This
is why your individual traits such as hair color or blood type may not
match those traits in either of your parents.
Ribosomal RNA
Ribosomal ribonucleic acid (ribosomal RNA or rRNA) helps to form the
ribosome itself. Unlike messenger RNA (mRNA), ribosomal RNA does not
transmit genetic information. Instead, it combines with proteins to
create a structure that systematically transforms mRNA into proteins.
The central dogma of cellular biology is that DNA is transcribed into
RNA, which is translated into proteins. The second step in this process,
translation, is performed by the ribosome. A ribosome intercepts mRNA,
which then requires specific amino acids to make the protein for which
it contains information. Ribosomal RNA forms a complex with various
proteins in order to bind the amino acids together.
Ribosomes can float freely in the cellular cytoplasm, or they can be
bound into a membrane called the endoplasmic reticulum (ER). ER that
contains ribosomes is called rough ER. Proteins produced in the rough ER
are transported through the ER to specific destinations. Ribosomes can
also appear in different sizes. Larger ribosomes simply contain repeat
copies of the same basic ribosomal RNA.
Ribosomal RNA appears as two separate parts which operate together. They
are the large subunit (LSU) and the small subunit (SSU). The LSU and
the SSU move smoothy in tandem along the strand of mRNA they are
translating. The LSU attracts transfer RNA (tRNA) molecules that carry
the necessary amino acids.
The part of the ribosome—at the meeting of the two subunits—that does
the work of joining amino acids is called peptidyl transferase. It is a
catalyst: it facilitates a chemical reaction by creating an environment
in which the reaction can easily take place. As such, it is called a
ribozyme, and is one of the few organic catalysts that is not a protein.
Living organisms contain several hundred copies of the genes required
for the two molecules of ribosomal RNA. This abundance and redundancy
reflect the crucial role that ribosomal RNA plays in supporting the
process of life. There is no known organism on Earth that would be able
to function without rRNA.
Ribosomal RNA is just as fundamental and widespread among bacteria as it
is in the animal kingdom. As a consequence, many antibiotics target
ribosomal RNA in bacteria. This rRNA is sufficiently unique that it can
be targeted without killing the infected organism, but also similar
enough among bacteria that individual antibiotics can kill many
different strains. Many of these antibiotics are naturally occurring
chemicals: products of the advantages bacteria can gain from killing
each other off independently!
DNA sexing
f you have an Eclectus parrot, there's no doubt about the sex of your
pet--the bright red female can hardly be mistaken for a green male. No
guessing with budgies, either, as a mature male's cere, the area just
above the beak, is blue. And in the case of canaries, you can hear the
difference--only males sing. In some cases, though, you can't tell just
by looking--or listening!
Do you know what sex your bird is? While many caretakers are content to
guess, others want to know with certainty if their beloved Max is really
a Maxine. And if you're considering adding another bird to your
family's flock, knowing your pet's gender can help you choose the most
compatible cagemates.
When the gender of a bird can be determined visually, he or she is a
member of a DIMORPHIC species. All members of MONOMORPHIC species,
however, look the same, and you cannot distinguish males from females
based on their appearance. The latter group includes macaws, conures and
cockatoos. Some species of lovebirds are monomorphic, while others,
such as the Abyssinian, are dimorphic.
If your avian companion is monomorphic, however, your pet's identity
need not remain a mystery. Many avian caretakers choose to have their
birds surgically sexed. After anesthetizing the bird, a veterinarian
makes a small incision in the abdomen and is thus able to view the
animal's internal sex organs. This procedure is safe and quick when
executed by an experienced doctor, but is not recommended for very young
birds. As they have not yet reached sexual maturity, their sex organs
are much more difficult to distinguish.
Up until recent years, this invasive procedure was the only reliable
method available. Thanks to the advent of DNA sexing, however, birds can
be accurately sexed without the possible complications of surgery and
anesthesia. A blood sample is collected from a vein or toenail--a
procedure that can be done easily and painlessly by the bird's
caretaker--and sent via mail to a laboratory, where it is analyzed to
determine the bird's sex. Unlike surgical sexing, DNA sexing can be
accurately done on baby birds. Another advantage is that your pet will
not have to leave the comfort of his environment--and that's less stress
for both you and your feathered friend!
DNA sexing services are currently offered by a number of laboratories
worldwide. First on the scene was Zoogen Services located in Davis, CA.
Zoogen was founded in 1990, and to date has accurately sexed over
330,000 birds. In the beginning, the analysis process was somewhat
cumbersome, taking about a week to complete.
parrot dna
Only one drop of blood is needed to determine the sex of a parrot. The
blood is collected in a capillary tube which is like a tiny glass straw.
Enzymes (a protein that serves as a chemical catalysts that is released
at the end of the reaction, so it may be used again) in the blood,
start to break down the DNA (deoxyribonucleic acid - the genetic
material that all living things inherit from their parents) as soon as
the sample is taken. The sample is immediately placed in a preservative
solution. The Zoogen instructions tell you to use rubbing alcohol, 70-
ethanol, gin or vodka in case you lose the preservative provided by
them.
In my Biology II class, I ran DNA isolations on calf liver. Additives
such as .09- solution of Sodium Chloride (salt water) are used to
liberate proteins and to remove undissassociated nucleoproteins
(proteins associated with the nucleus where the DNA is found). I added
Sodium Dodecylsufate (SDS) which acts as a biological detergent to cut
through oil and to dissolve the membrane surrounding the nucleus so the
DNA could be retrieved.
At Zoogen, solutions are added to the sample. They are shaken and
centrifuged to separate the solution into several layers. Heavier
particles go to the bottom and lighter particles rise to the surface.
The DNA can be removed at this point and is a very thick, sticky small
mass. This step could take about a day to complete. More isolation
procedures are run to further dissolve the DNA which could take another
10 hours.
The isolated DNA is next dissolved in another solution containing
enzymes called restriction enzymes. In nature, these enzymes protect
against intruding DNA. They work to cut up foreign DNA restricting it
from surviving in your own cells. These enzymes recognize short
nucleotide (an organic unit consisting of a sugar molecule bonded to a
nitrogen base and a phosphate group - - nucleotides are the building
blocks of nucleic acids) sequences in DNA molecules and cut them at
specific points within the so-called recognition sequences. These pieces
of DNA are called restriction fragments. The differences in homologous
DNA sequences that result in restriction fragment lengths have been
dubbed restriction fragment length polymorphisms or RFLPs (pronounced
riflips). This procedure is used by thousands of labs over the last ten
years to examine DNA. It is a well-known tool of gene analysis and is
not experimental. Correctly done, DNA doesn't lie. I guess you can tell I
watched a lot of the Simpson Trial.
The DNA fragments are then placed near one end of a bed of gel that has
an electric current running through it. The DNA is negatively charged
and moves to the positive end of the gel. Smaller fragments move faster
than large ones. After about 18 hours, the fragments are arranged by
length. This procedure is called electrophoresis. When the DNA has been
run out (separated by length sizes) the gel is exposed to UV light. At
this point, the DNA can actually be seen (it glows because of the
chemicals added to it). The DNA (a double strand-stranded helical giant
molecule - it looks like a twisted ladder) can be "unzipped" or split
into two complementary strands. These splits are transferred to a nylon
membrane. The nylon membrane is immersed in a bath and a radioactive
probe. The probe is actually a stretch of DNA of a known sequence. The
species (breed) of the bird is necessary so they can use the correct
probe in identifying the sex of the bird. If you do not put the correct
species on, the test could be delayed or perhaps be incorrect. The
technicians can usually tell if you reported the wrong species, because
they can recognize most species' patterns. After having run over 90,000
samples, they have a lot of experience reading these results. The probe
seeks out the complimentary strands of DNA and bonds to it. They know
what the probe is and the places to which it will bond. Those places are
associated with pieces of DNA on the bird's sex chromosomes. The last
step is to expose x-ray film to the nylon membrane containing the
radioactive probe. Dark bands develop at the probe sites. The resulting
X-ray is a pattern which can be interpreted by technicians. The pattern
of these bands reveal the sex of your bird. Many animals, including
humans, have a pair of sex chromosomes, designated X and Y, that
determine an individuals sex. In humans, individuals with XY chromosomes
are male and XX chromosomes are female.
The sex of a human baby is determined by the father whether they get an X
or a Y. In contrast to this system, birds have sex chromosomes
designated Z and W. Males have ZZ and females are ZW. These are the
chromosomes used in the DNA sequence probe to determine the sex of a
bird. In birds, the female determines the sex of her offspring whether
they get Z or W chromosomes. Isn't science wonderful? Now you know how
DNA sex determination works. I think you really get a lot of technology
for your money.
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Cloning, the copying of the same basically means anything . Genetikde , a
particular section of DNA , often used to create copies of a gene is
the method . DNA fragments generated in this way , is used in research .
with her husband in the DNA of an organism , the method used to create a
new life often called " somatic cell nucleus transfer "is called.
cloning in the biological sense , single-celled organisms is a form of
reproduction ( clonal growth ). Apart from these specific issues in
multicellular organisms, specialized cells that divide to form
themselves again, " Clonal reproduction is called . The best examples
are the human immune system cells . against a specific effect of these
cells to recognize pathogens , capable of producing the right antibodies
as cell clonal proliferation of war and disease are .
" Cloning " begins to be heard by the masses of the concept in 1997,
Scottish scientists at Roslin Institute , Dr . Wilmut and his team the
sheep " Dolly , " I began to produce . Part of the worldwide interest in
scientific development view , some of which are due to ethical problems
. In fact, much earlier than the foundation for cloning , based on
studies with bacteria .
based cloning can be divided into the three main headings :
* Recombinant DNA technology
* Çoğaltımsal cloning
* Therapeutic cloning Purpose
Messenger RNA (mRNA)
stored in DNA The genetic information , protein structure acts as an
intermediary in transferring a molecule Okoume . Copies can be solved by
DNA extracted molecules are localized . Messenger ribonucleic acid ,
called m - RNA , DNA from a specific carries the information of chemical
structures have been translated into polypeptide . m - RNA nucleotides,
and a single strand of DNA consists of patterns in the neck . On the
nucleotide sequence of the DNA helix is one of the matches . Polypeptide
molecules , DNA was separated from the m - RNA into ribosomes sticks ,
here are proteins produced in accordance with the incoming messages .
RNA molecules are combined in this way , just like a photo negative of
the positive and the co- inheritance case is the type of message across .
With these messages can be solved later in the cytoplasm, ribosomes and
amino acids through a combination of carrier will be used for RNA.
What is RNA ?
ribonukleotitlerinbirbirlerine RNAs are single-stranded nucleic acid
with the binding is occurring . DNA
When compared with molecular length is shorter. In almost all cells as
abundant
are present . DNA protein production to fulfill the function of a "call
molecules " to
is needed. This function is loaded ribonucleic acid sequence of
nucleotides settling corporate
Consisting of a single series ( such as DNA single strand of chain ) is a
high -quality molecules . DNA
molecules were found largely in the cell nucleus , are of RNAs into
cells have spread .
usually double- helix structure of DNA in the lane , while the single
şerittlidir RNA . However , DNA single -lane and double lane
RNA molecules are seen as well
Gene transfer
Gene transferAn organism's cells , another organism's DNA is called to
the replacement of certain parts .
One of the applications of gene transfer is gene therapy . Today ,
however, many plants and animals through gene transfer is a new feature
win .
Dolly the sheep is the first that shows the importance of gene transfer .
Gene transfer can be achieved thanks to better health for future
generations .
DNA replication
DNA replication or DNA synthesis, the double- stranded DNA before cell
division is the process of copying . new DNA strands are copied almost
exactly the same , but from time to time due to errors in replication is
not a perfect copy (see mutation) , and the results of both the helix
consists of an old and a new thread . It is called semi- conservative
replication . DNA replication consists of three steps : initiation , two
recovery and termination
Recombinant DNA ..
Recombinant DNA or Recombinant DNA technologyOften obtained from
different biological species of DNA molecules , genetic engineering and
the cessation of DNA fragments obtained from different biological
processes and combining the results of this process produced the name
given to the new DNA molecules .
Recombinant DNA technology is used in many fields .
Recombinant DNA technology is used in many fields .
Genetic recombination events artificially realization is based on
recombinant DNA technology ( rDNA ), the first work in 1973 has started ,
and 80 in the giant steps forward , and today, the name most frequently
mentioned , and molecular genetic revolution has created a science has
become
What is DNA
DNA, or deoxyribonucleic acid, is the hereditary material in humans and
almost all other organisms. Nearly every cell in a person’s body has the
same DNA. Most DNA is located in the cell nucleus (where it is called
nuclear DNA), but a small amount of DNA can also be found in the
mitochondria (where it is called mitochondrial DNA or mtDNA).
The information in DNA is stored as a code made up of four chemical
bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human
DNA consists of about 3 billion bases, and more than 99 percent of those
bases are the same in all people. The order, or sequence, of these
bases determines the information available for building and maintaining
an organism, similar to the way in which letters of the alphabet appear
in a certain order to form words and sentences.
DNA bases pair up with each other, A with T and C with G, to form units
called base pairs. Each base is also attached to a sugar molecule and a
phosphate molecule. Together, a base, sugar, and phosphate are called a
nucleotide. Nucleotides are arranged in two long strands that form a
spiral called a double helix. The structure of the double helix is
somewhat like a ladder, with the base pairs forming the ladder’s rungs
and the sugar and phosphate molecules forming the vertical sidepieces of
the ladder.
An important property of DNA is that it can replicate, or make copies of
itself. Each strand of DNA in the double helix can serve as a pattern
for duplicating the sequence of bases. This is critical when cells
divide because each new cell needs to have an exact copy of the DNA
present in the old cell.
Types of skin cancer
Keratinocyte cancers
These are by far the most common skin cancers. They are called keratinocyte carcinomas or keratinocyte cancers because
when seen under a microscope, their cells look like early forms of
keratinocytes, the most common type of skin cell. Most keratinocyte
cancers are basal cell carcinomas or squamous cell carcinomas.
Basal cell carcinoma
This is not only the most common type of
skin cancer, but the most common type of cancer in humans. About 8 out
of 10 skin cancers are basal cell carcinomas (also called basal cell cancers). When seen under a microscope, the cells in these cancers look like cells in the lowest layer of the epidermis, called the basal cell layer.
These cancers usually develop on sun-exposed
areas, especially the head and neck. Basal cell carcinoma was once
found almost entirely in middle-aged or older people. Now it is also
being seen in younger people, probably because they are spending more
time in the sun.
These cancers tend to grow slowly. It’s very
rare for a basal cell cancer to spread to other parts of the body. But
if a basal cell cancer is left untreated, it can grow into nearby areas
and invade the bone or other tissues beneath the skin.
After treatment, basal cell carcinoma can
recur (come back) in the same place on the skin. People who have had
basal cell cancers are also more likely to get new ones elsewhere on the
skin. As many as half of the people who are diagnosed with one basal
cell cancer will develop a new skin cancer within 5 years.
Squamous cell carcinoma
About 2 out of 10 skin cancers are squamous cell carcinomas (also called squamous cell cancers). The cells in these cancers look like abnormal versions of the squamous cells seen in the outer layers of the skin.
These cancers commonly appear on sun-exposed
areas of the body such as the face, ears, neck, lips, and backs of the
hands. They can also develop in scars or chronic skin sores elsewhere.
They sometimes start in actinic keratoses (described below). Less often,
they form in the skin of the genital area.
Squamous cell cancers are more likely to
grow into deeper layers of skin and spread to other parts of the body
than basal cell cancers, although this is still uncommon.
Keratoacanthomas are dome-shaped
tumors that are found on sun-exposed skin. They may start out growing
quickly, but their growth usually slows down. Many keratoacanthomas
shrink or even go away on their own over time without any treatment. But
some continue to grow, and a few may even spread to other parts of the
body. Their growth is often hard to predict, so many skin cancer experts
consider them a type of squamous cell skin cancer and treat them as
such.