Question

1)  Identify the polypeptide (Using the 3-letter abbreviations for amino acids) that would be produced as a result of transcribing and translating the following DNA sequence.

DNA: ...3' A C C A A G T C T 5'...

2)  The strand of DNA used above undergoes a mutation, such that the second C from the 3' end is changed to a T. What would change in the polypeptide?

3) List the different codons that can code for arginine.

Answer 1

1. Here the given DNA strand is template strand and the mRNA produced by template strand has complimentry sequence to the template strand thus, he corresponding mRNA will be UGGUUCAGA. Therefore the polypeptide sequence will be: Trp-Phe-Arg (UGG codes for Trp, GUU codes for Phe and AGA codes for arginine).

2. After mutation (2nd C changed into T) the DNA sequence will be ACTAAGTCT and the corresponding mRNA will be UGAUUCAGA. There will be no synthesis of polypeptide because here the first codon is UGA which is stop codon and thus, no polypeptide synthesis will occur.

3. The different codons which code for arginine are as follows: UGU, UGC, UGA, UGG, AGA and AGG.