Question

An interesting mutation is discovered in a species of wasp where the DNA sequence of the genome is unknown. In order to try to determine the molecular nature of this mutation, a geneticist treats mutant wasps with the chemical 5-bromouracil, a chemical mutagen that induces both types of transition mutations at high frequencies, and hydroxylamine, which induces only GC-to-AT transitions. Neither chemical mutagen caused the back mutation or reversion frequencies to increase beyond the low spontaneous values. Which of the following types of mutations is the least likely to be the original wasp mutation?

A. A-to-T
B. -1 frameshift
C. A-to-G
D. +1 frameshift
E. A-to-C

Answer 1

The original wasp mutation is least likely to be A-to-T. The chemical mutagens used in the experiment were 5-bromouracil and hydroxylamine.

Step-by-step explanation:

The original wasp mutation is least likely to be A-to-T. The chemical mutagens used in the experiment were 5-bromouracil and hydroxylamine. 5-bromouracil induces both types of transition mutations, while hydroxylamine induces only GC-to-AT transitions. If the original mutation was A-to-T, then treating the mutant wasps with hydroxylamine would have caused an increase in back mutation or reversion frequencies. However, this did not occur, indicating that A-to-T mutation is the least likely to be the original mutation.