Question

Which of the following mutations would likely have the most dramatic effect on protein structure, and why? Which would likely have the least dramatic effect?  

a. changing one purine for another in the first position of a codon.

b. changing one pyrimidine for another in the second position of a codon.

c. changing a purine with a pyrimidine in the second position of a codon.

d. changing a pyrimidine for another pyrimidine at the third position of a codon.

PLEASE DO NOT FORGET TO EXPLAIN YOUR REASONING, AT LEAST BRIEFLY. Otherwise, I am not learning anything. I want to be able to understand your answer :)

Answer 1

. The answer is accordingly to the wobble hypothesis which state that when the third base in the triplet coding will change, then it will not be able to interact with anticodon which is present at tRNA. First two bases of Codon have hydrogen bond with two bases in anticodon but the third base of Codon can undergo unusual base pairing. Hence, the least dramatic effect will be observed at third position. Hence for that option "d" is correct whereas changing in the base of Codon from purine to pyridimine will change the corresponding amino acid in the protein. Hence, most dramatic effect will seen in this condition. Hence, option "C" is correct for this situation.