Text of DNA Replication & Protein Synthesis. DNA REPLICATION
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DNA Replication & Protein Synthesis
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DNA REPLICATION
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DNA Replication When cells divide, they need the instructions
on how to be a particular type of cell and how to function as that
cell type. These instructions are found in the DNA of the parent
cell. It has its own full set of DNA instructions. When the cell
divides to form two cells it must make sure the new cell has a full
set of DNA as well. If one cell is to become two cells then one set
of DNA must become two sets this is replication its a part of
mitosis.
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Semiconservative? Semi = half Conserve = to keep
Thereforesemiconservative literally means half is kept. This means
that we will use the old DNA as a template to make two new DNA
molecules. Each new DNA molecule is therefore made up of one strand
from the old DNA and a newly synthesized strand of DNA that match
up according to the base- pair rule.
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Replication The Process Replication is a two-phase job
1.Separate the old strands. 2.Build the new (complementary)
strands. To perform these jobs we will use a number of enzymes and
free-floating DNA nucleotides that we would have gotten into the
cell when we ate the cells of another organism for breakfast or
lunch. Your DNA may have once been used in a dinosaur or bacterial
cell it all recycles.
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DNA Replication
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PROTEIN SYNTHESIS
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DNA RNA Pn DNA RNA Pn is known as the central dogma of modern
biology. The process it illustrates is protein synthesis. Proteins
build, operate and regulate the body pretty important stuff! In
fact, the word protein means of primary importance! DNA
(deoxyribonucleic acid) resides in the nucleus of your cells and it
carries all of the instructions on how to build your proteins. This
is why it is called the blueprint of life. DNA is the blueprint and
proteins are the structures made using the blueprint. So what is
the role of the RNA?
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Why RNA? RNA (Ribonucleic acid) is the link between DNA and
proteins. DNA lives in the nucleus its the boss that works in the
head office of the cell it never leaves that office! Proteins are
built by little organelles called ribosomes which live in the
cytoplasm of the cell not the nucleus. RNA is what helps connect
the DNA in the nucleus to the ribosomes in the cytoplasm. Think of
RNA as the messenger. It carries the instructions from the DNA, in
the nucleus, out to the protein-building ribosomes, in the
cytoplasm. DNA RNA Pn (It makes more sense now eh?)
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Transcription (DNA RNA) The first step in protein synthesis is
transcription. It takes place in the nucleus of the cell.
Transcript = copy. The DNA is going to unwind and make a copy of
one small section of itself. This small section is a gene one trait
about you. This small copy of the DNA is called mRNA (messeneger
RNA). It carries the code for one gene on the DNA out to the
cytoplasm. Transcription is complete once the mRNA has been
constructed. The mRNA will travel through one of the pores in the
nucleus out to the cytoplasm in search of a ribosome.
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Transcription
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Translation (RNA Pn) Translation is the second step of protein
synthesis. It occurs in the cytoplasm when the mRNA is used by the
ribosome to build the protein. A translator is someone who takes
one language and changes it into another language. The name
translation applies here because the ribosome is using a nucleic
acid sequence to build a protein sequence. It is changing the
sequence of one type of biomolecule into a sequence of
another.
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Translation (RNA Pn) Translation begins when the ribosome (the
protein builder) finds the mRNA and sits on one end of the mRNA
strand. The ribosome then begins moving along the mRNA, reading the
nucleotide sequence (As, Cs, Gs & Us). It uses this sequence to
help it gather the proper amino acids (protein building blocks) and
put them in order in the newly made protein. Once the ribosome
reaches the end of the mRNA it jumps off and releases the newly
made protein. The protein can now go and do some work in the
cell.
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Translation The ribosome (green blob) is traveling down the
mRNA strand (blue line) and reading it. The code on the mRNA strand
tells the ribosome which amino acids (yellow ovals) are needed to
build the protein (all the yellow ovals connected together).
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Polysomes A polysome occurs when a number of ribosomes are
translating the same piece of mRNA at the same time. This gives you
many copies of the desired protein using only one mRNA. This saves
the cell energy and resources.
