Question

In ATG ACC AGG ACC CCA ACA sequence, the first base gets mutated. It will affect

• A. Change in types and sequence of amino acids
• B. Change in first amino acid only
• C. No change
• D. One amino acid less

Answer 1

The correct option is B Change in first amino acid only

According to the question, a mutation in the first base (Adenine) can change the codon specifying a different amino acid by substitution of one base (missense mutation). The transition of adenine to guanine changes the first codon from ATG to GTG; transversion of adenine to cytosine or thymine change the codon from ATG to CTG or TTG respectively. The insertion of one or more nucleotide base shift the reading frame forward and deletion of one or more nucleotide base shift the reading frame backward which in turn changes types and sequence of amino acids. Thus there is a change in first amino acid; the whole frame is not affected which makes options A and C incorrect and B correct. Deletion of a base shift the frame forward and the resultant protein is one amino acid less; here the base is changed not deleted; option D is incorrect.

The correct answer is B.