Answer
d.
Work Step by Step
Option a. is incorrect. The mRNA molecule should have uracil instead of thymine.
Option b. is incorrect. According to the mRNA sequence given, there is no single-base mutation.
Option c. is incorrect. The mRNA sequence given has several mutations, not just a single-base.
Option d. is correct. The single-base mutation occurs where you see the first adenine (A). That adenine should have been a cytosine (C) instead.
