17. In a certain mutant strain of bacteria, the enzyme leucyl-tRNA synthetase mistakenly attaches isoleucine to leucyl-tRNA 10% of the time instead of attaching leucine. These bacteria will synthesize:

Question

A. no abnormal proteins, because the ribosomal translation machinery will recognize the inappropriately activated tRNAs and exclude the from the translation process.
B. no proteins, because the inappropriately activated tRNAs will block translation.
C. proteins in which leucine is inserted at some positions normally occupied by isoleucine.
D. proteins in which isoleucine is inserted at some positions normally occupied by leucine

Answer 1

The correct answer is:

D. proteins in which isoleucine is inserted at some positions normally occupied by leucine.

Explanation: Since the enzyme leucyl-tRNA synthetase improperly attaches isoleucine to leucyl-tRNA, when this tRNA encounters the ribosome during protein synthesis, it will be recognized as a tRNA carrying leucine. As a result, isoleucine will be incorporated into the growing polypeptide chain at positions where leucine is supposed to be, potentially leading to proteins with some substitutions of isoleucine in place of leucine.