Question

A mutation in the tRNA for the amino acid lysine results in the anticodon sequence 5'-UAU-3' (instead of 5'-UUU-3'). Which of the following aberrations in protein synthesis might this tRNA cause?

A) read-through of stop codons
B) substitution of lysine for tyrosine.
C) substitution of lysine for isoleucine
D) substitution of lysine for phenylalanine

Answer 1

A tRNA mutation resulting in an anticodon change to 5'-UAU-3' would lead to the substitution of lysine for isoleucine (C) in the protein, because the new anticodon would now bind to the codon AUA which encodes for isoleucine.

Step-by-step explanation:

A mutation in the tRNA for the amino acid lysine has resulted in an anticodon 5'-UAU-3' instead of the normal 5'-UUU-3'. In mRNA, the codon complementary to 5'-UAU-3' is 3'-AUA-5', which codes for isoleucine, not lysine. Therefore, the aberration in protein synthesis that this tRNA mutation would cause is the substitution of lysine for isoleucine (C).

Normally, the tRNA molecule with the anticodon UUC binds to the codon AAG in mRNA, which codes for lysine, during protein synthesis. Due to the mutation in the tRNA anticodon to UAU, the tRNA would instead bind to an AUA codon on the mRNA, causing lysine to be incorporated where isoleucine should have been, potentially resulting in a mutation known as a missense mutation and altering the structure and function of the protein being synthesized.