Point mutation, change in rna and protein

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Discussion Overview

The discussion revolves around the effects of point mutations induced by UV rays on DNA sequences, specifically focusing on how these mutations may alter mRNA and protein sequences. The scope includes homework-related queries about genetic mutations, their implications, and the interpretation of coding sequences.

Discussion Character

  • Homework-related
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the insertion of a nucleotide "T" after a bolded "G" results in a frameshift mutation, leading to completely different mRNA and protein sequences, but expresses uncertainty about this conclusion.
  • Another participant requests clarification on what the changed protein sequences would be in both cases of nucleotide insertion.
  • A third participant states that since the mutation occurs after a stop codon, it may not affect the protein sequence, indicating that there might be no change in the protein sequence.
  • One participant raises a question about the ambiguity of the coding sequence, noting that the start codon location is crucial for determining the impact of the mutation.
  • Several participants express confusion about how to answer the assignment question and seek guidance on whether to contact the instructor for clarification.
  • Another participant discusses the probability of the question appearing on a test and questions the validity of their logic in answering it without further guidance.

Areas of Agreement / Disagreement

Participants express differing views on whether the mutations will change the protein sequence, with some suggesting no change due to the position of the stop codon, while others argue that frameshift mutations will alter the sequences. The discussion remains unresolved regarding the exact implications of the mutations.

Contextual Notes

There is uncertainty regarding the definition of the coding sequence and the implications of the mutations, as well as the potential impact of the stop codon on the overall protein sequence. The discussion does not clarify these aspects fully.

Who May Find This Useful

Students studying genetics, molecular biology, or related fields may find this discussion relevant, particularly those working on assignments related to DNA mutations and their effects on protein synthesis.

Raghav Gupta
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Homework Statement



UV Rays is said to induce point mutations which get incorporated during the DNA replication process. These mutations are corrected by the excision repair mechanism of the DNA polymerase but sometimes they might be left out. In one of such cases, point insertions were incorporated. The DNA sequence is given as under
5'GTGTCCGTCTAATATTGTGAGATGTTATATCCCGCCGTCAACACCATCAACAGGATAATCGCCTGCTGGGGCAAAGGCGGTGAAG 3’
i) The nucleotide “T “is inserted after the “G” which has been bolded. Will the mRNA and the protein sequence change?
ii) The nucleotide “T” is inserted after the bolded “T”. What are the changes in mRNA and the protein?
2.

Homework Equations


Can't think for this question which is applicable.

The Attempt at a Solution


It is looking to me a frameshift mutation in both cases, so there will be completely different mRNA and proteins form. But I do not know properly that what I am thinking is correct or not.
 
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Can you say what the changed protein sequence will be in each case?
 
Ygggdrasil said:
Can you say what the changed protein sequence will be in each case?
The original protein sequence is:
Valine- Serine- Valine- Stop-......etc.
But, we should not go further since the stop codon UAA comes.
Here in question 5'...3' dna strand is non-template strand and mRNA sequence would be that of strand by substituting U in place of T.
Mutation is anyway taking place after that codon, so it does not matter.
So these answer my both questions that is no change in protein sequence?
So to this question, only this much answer?
 
It depends which part of the sequence is considered the coding sequence. For example, there is a start codon further down. Is that AUG the start of the coding sequence or is the stop codon at the beginning the end of the coding sequence? It's unclear from the information you've given.
 
So how do I answer this question?
It was given to us as an assignment and I am having confusion.
 
Ask your instructor for clarification.
 
If this question comes in test, having probability of coming 1/5, is my logic of answering correct? I don't have a class with my instructor till the test takes place.
Or should I mail him this question, though don't know if someone answers in a mail subject questions and it is not good to ask in a mail.
 

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