Which Mutation Shortened the Peptide? - USMLE Forums
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Old 04-13-2010
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Question Which Mutation Shortened the Peptide?

A normal peptide has 100 amino acids. Following mutation, it has only 20; 1–10 are the same as the normal peptide; 11–20 differ from the normal peptide. Which of the following mutations occurred?

(A) Nucleotide deletion in the codon for amino acid 11 (codon 11)
(B) Nucleotide deletion in codon 20
(C) Nucleotide deletion in the intervening sequence
(D) Nucleotide substitution in codon 11
(E) Nucleotide substitution in codon 20
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  #2  
Old 04-13-2010
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Default So difficult

It seems that nobody dare to answer this question
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Old 04-13-2010
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Not sure, but may be option A.
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Old 04-13-2010
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Default Answer

the correct answer is A.
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Old 04-13-2010
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Default

Alrite this is my take on it:

This is a frame shift mutation that resulted at a stop codon at position 20. Therefore, it can't be a substitution and has to be a deletion so that leaves A, B, or C

B could result in a shortened chain but the change would be after position 20.

C would result result in a misense mutation and not necessarly a truncated protein as much as a non-functional one.

So the only thing left is A would would cause the frame shift mentioned above.
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Old 04-14-2010
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Default haha

yes the answer is A. unfortunately i dont have the explanation for it. so if anyone could explain y pls??
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Old 04-14-2010
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Default The explanation is there

Quote:
Originally Posted by Seetal View Post
yes the answer is A. unfortunately i dont have the explanation for it. so if anyone could explain y pls??
Did you read housewannabe answer! He explained it very nice.
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