using the dagram below, describe the process of translation. Label the diagram t
ID: 182366 • Letter: U
Question
using the dagram below, describe the process of translation. Label the diagram the best you codnd 1 OTHER QUESTIONS What are the 3 possible outcomes of point mutations? Describe what each means. Consider the codon UCG. Create a neutral mutation. Create a nonsense mutation. Create a missense mutation. What is a frame shift mutation? Why are frame shift mutations usually more deleterious (worst) than a point mutation? If all the cell in our body have the same set of genes, why are the liver cells not the same as the brain cells?Explanation / Answer
The central dogma in molecular biology explains a two step process that includes transcription and translation.
Transcription is the process of formation of RNA (ribo nucleic acid) from DNA (deoxy ribo nucleic acid).
The process of synthesis of proteins from the information contained in RNA is known as translation.
The above given diagram explains the process of translation.
Translation is the process in which mRNA is decoded to synthesize the protein that contains a specific series of amino acids.
The key molecules for translation are tRNA (transfer RNA) and ribosomes.
Translation is a step wise process, which proceeds through the three major steps that are shown in the given diagram. They are:
1. Initiation
2. Elongation
3. Termination
1. Initiation of translation:
mRNA has the code for protein. The code presant on mRNA is decoded into amino acids. The nucleic acids present on mRNA are read as triplet codon (triplet codon is a group of three nucleotides).
The ribosomes assemble around the mRNA and the codon present on mRNA are read by tRNA. One end of tRNA contains an anti-codon and the other end contains the corresponding amino acid.
In the first step of translation (initiation) an initiation complex is formed by mRNA, ribosome and a tRNA molecule.
AUGis the start codon which codes for the aminoacid methionine. tRNA carrying methionine binds to the start codon (AUG) and translation initiates.
2. Elongation of translation:
The second step of translation is elongation.
This is the stage where extension of polypeptide chain takes place.
One triplet codon on mRNA is read once and tRNA carrying the corresponding amino acid binds to the mRNA.
The existing amino acid chains links to the amino acid on tRNA through a chemical reaction. At each step one amino acid is added to the polypeptide chain and the elongation continues.
As elongation proceeds, the next triplet codon is exposed.
3. Termination of tranlation:
Termination is the final stage of translation in which the polypeptide chain is released. Elongation continues till the stop codons are exposed on mRNA.
There are three stop codons. They are: UAA, UAG and UGA.
When the stop codon is reached, the ribosome releases the polypeptide.
Answers to the other questions:
Point mutation is a genetic mutation that occurs when a single nucleotide base is changed.
A point mutation may occur as a result of insertion or deletion or a change of a single nucleotide base from the DNA or RNA.
The pont mutations are of three types. They are :
1. Base-pair insertions
2. Base-pair deletions
3. Base-pair substitutions
The point mutations are small scale mutations which may result in silent mutation, mis sense mutation or non-sense mutation. These are the three outcomes of point mutations.
1. A silent mutation is the type of point mutation in which the change in a single nucleotide base does not cause any change in the protein produced by the gene. This happens due to the reason that multiple codons are there to code for a single amino acid.
For example CUU, CUA, CUG and CUC code for leucine. Thus if there is a single base change at the third position of any of these triplet codons, they code for leucine only.
2. Mis-sense mutation is a kind of mutation in which a single base change results in the change of a single amino acid of the polypeptide.
Example: UCU codes for serine. If U is replaces by C, CCU codes for proline.
3. Non-sense mutation is a kind of point mutation in which a single nucleotide base change results into a stop codon which terminates the translation.
For example: UAC codes for tyrosine. If C is substituted by A, it results in UAA which is a stop codon.
Answer to next question:
UCG codes for the amino acid serine.
Condition 1: Neutral mutation is nothing bu silent mutation, which is explained above.
UCG is changed to UCA due to substitution, which also codes for serine. Hence it is a neutral mutation.
Condition 2: If UCG is changed to UAG due to substitution, it is a non-sense mutation because UAG is a stop codon.
Condition 3: If UCG is changed to ACG due to substitution, it is a min-sense mutation. Because ACG codes for the amino acid threonine. If one amino acid of the polypeptide is changed, it is considered as the min-sense mutation.
Answer to the next question :
Frame shift mutation is a kind of genetic mutation in which a number of nucleotides are changed in DNA due to insertion or deletion. Frame shift mutations are more deleterious than point mutations because these are large scale mutations. Unlike the point mutations, frame shift mutations alters the polypeptides drastically.
The entire frame of triplet codon is changed in frame shift mutations.
Some times such mutation may result in alteration of stop codon also, which may result in continued elongation of polypeptide.
If the frame shift happens in such a way that the stop codon occurs too early, such condition results in termination of translation too early.
Hence such mutations may result in too long polypeptides or too short polypeptides which are abnormal.
Frame shift mutations leads to deleterious diseases like: cystic fibrosis, Crohns disease, Tay-Sachs disease, Smith-Magenes syndrome etc.
Answer to next question:
Though all the cells in our body have same set of genes, cells of different organs are different. This is because of the differential gene expression in different organs and different tissues.
The gene expression is different in different organs. The liver cells have different proteins and brain cells have different proteins. The required proteins and enzymes are synthesized based on their functions.
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