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Genetic Code, Transcription, & Translation
Transcript of Genetic Code, Transcription, & Translation
Genetic Code, Transcription, & Translation
By:Arthur W. Ruby H. & Dustin M.
1 December, 2017
the action by which instruction/information in DNA is duplicated into messenger RNA for protein production.
activator proteins that connect to specific sets of DNA
roteins connect to enhancer regions that initiate the process of transduction
-Only one of the strands is copied which acts as an example for the synthesis of an RNA molecule which is assembled one sub-unit at a time by matching the DNA letter code on the example strand.
-The sub-units enter the enzyme through its intake hole and they are conjoint to form the long messenger RNA chain snaking out of the top.
- To completely understand the process of Transcription and know all of the tools used that function in Transcription.
-To get a general idea of what how mRNA is produced to an in depth scale.
The genetic code is the rules that tells us how the information that is encoded into our genetic material is translated into proteins by cells that are in our body.
The simple break down is:
The genome of an organism is inscribed in DNA, the portion of the genome that codes for protein or RNA is referred to as a gene.
These genes are each composed of codons, each of these codons then code for a single amino acid.
The end results in proteins that are vital to our bodily function.
The genetic code produced proteins that obviously have to start and stop somewhere.
The basic function of translation is decoding a messenger RNA and using that information in order to create a polypeptide.
So how do these condons match up to create polypeptide chains?
Each tRNA has an anticodon, a set of three nucleotides that bind to a matching mRNA codon through base pairing.
The other end of the tRNA carries the amino acid that's specified by the codon.
In translation, the codons of an mRNA are read in order (from the 5' end to the 3' end)
Parts of the Genetic Code
In 1953 Watson and Crick discovered the structure and properties of DNA
Failed to answer how the DNA strand translated into a protein.
The linear sequence of nucleotides in DNA are A , T, G, and C (adenine, thymine, guanine, and cytosine).
The first attempt by George Gamow.
Founded the "RNA Tie Club". The aim was "to solve the riddle of the RNA structure and to understand how it builds proteins.
Gamow used mathematics to determine that a three-letter nucleotide code would be enough to define all 20 amino acids, with 64 different combinations. 61 encode amino acids and 3 specify termination of translation (these are otherwise known as stop codons.
Nirenberg and his colleague Johann H. Matthaei used a
where, in a test tube they put together all the things that were needed for protein synthesis: RNA template, ribosomes, nucleotides, amino acids, stabilizing agents, and energy.
They carried out a series of experiments to see what amino acid a particular combination of nucleotides created.
They made a very simple nucleic acid, which was composed of only one single repeated letter, uracil (U).
And by using U they were able to produce a protein that also contained a single letter, F or phenylalanine.
The next codon that was discovered was CCC or cytosine repeated which is the template for the amino acid proline or P.
How do these chains form?
There are three different sites on the free ribosomes.Ribosomes are composed of three subunits.
The A-site, P-site and E-site.There is one binding site for mRNA and three for tRNA.
A-site (acceptor) binds to the aminoacyl tRNA, which holds the new amino acid for it to be added to the chain.
P-site (peptide) binds the tRNA to the polypeptide chain.
E-site (exit) serves as the final step where the tRNA is detached.
Har Gobind Khorana's Experiment
Devised a precise and intricate biochemical method that would produce well-defined nucleic acids, long stands of RNA with every nucleotide in its exact position.
First one one a strand of the repeating letters UCUCUC... which then translated to serine-leucine-serine-leucine-serine...
Robert Holley's Contribution
He was able to work out the exact structure of the genetic code in 1965.
He was a chemist that had learned about protein synthesis one summer and it led him to discover the special type of nucleic acid called transfer RNA or tRNA.
The bacteria E.coli was widely used in testing.
The Universal Genetic Code
The genetic code is universal in the sense that any organism will have the same process when it comes to protein synthesis.
There will be some rare exceptions to this rule but the differences from the genetic code will be very small. One such exception will be RNA in mitochondrial DNA where UGG and UGA encode for Trp. The UGA is the small change.
In order to start the use a start protein in a process called initiation. The major codon that identifies with most proteins is AUG. In between will be all the amino acids that builds the protein, this process is called elongation. While the protein continues to grow it becomes a non overlapping sequence where there will be kinks and and turns in on itself. Means that there is no "breaks" or "doubles" And when the protein is finished there will be three stop codons. These will most commonly have the letters UAA, UAG, of UGA.
There are three main phases in translation. Initiation, Elongation and Termination.
In the beginning, tRNA starts in the middle slot of the ribosome, called the P site. Next to it, a fresh codon is exposed in another slot, called the A site.
The A site will be the "landing site" for the next tRNA, one whose anticodon is a perfect match for the exposed codon.
Once the matching tRNA has landed in the A site the formation of peptide bonds begins; they connect one amino acid to another. This step transfers the methionine from the first tRNA onto the amino acid of the second tRNA in the A site.
Translation ends in a process called termination. Termination happens when a stop codon in the mRNA (UAA, UAG, or UGA) enters the A site.
Stop codons are recognized by proteins called release factors, which fit neatly into the P site. Release factors mess with the enzyme that normally forms peptide bonds.It adds a water molecule to the last amino acid of the chain. This reaction separates the chain from the tRNA, and the newly made protein is released.
To make a protein, ribosomes link together amino acids.
The mRNA has the specific order in which the amino acids must be joined, and each protein has a different order of amino acids.
The small subunit of rRNA can read the order of amino acids.
Linking amino acids together is the function of the rRNA in the large subunit of the ribosome.
Stages of Translation:
- To introduce the topic of the genetic code.
- To provide the history of the genetic code and how it was founded.
- To provide the general process of protein synthesis.
-Transcription is the action by which instruction/information in DNA is duplicated into messenger RNA for protein production.
-Transcription starts off with a bundle of two transcription factors at a specific promoter region along the DNA and a mediator protein complex arrives carrying the enzyme RNA polymerase.
-Transcription is initiated when the mediator protein later comes in contact with other activator proteins that connect to specific sets of DNA (Enhancer regions)
-When initiated, the RNA polymerase quickly runs along the DNA which activates the copying mechanism, the RNA polymerase unzips a small portion of the DNA helix exposing the bases on each strand.
What is the purpose of transcription?
-Transcription is what produces mRNA which is a copy of a strand for DNA
-mRNA is later used in another process known as Translation, it is like the puzzle piece that matches everything together
Why is Transcription such an important process?
-Without transcription, duplication of DNA would not exist and therefore coding for a specific organism wuld not occur.
-Translation is a step in protein biosynthesis wherein the genetic code carried by mRNA is decoded to produce the specific sequence of amino acids in a polypeptide chain.