Question

3) A mutagen has introduced a frame-shift mutation by adding one nucleotide base. Which of the following would be classified as a reversion mutation for this particular mutant? A) deleting 2 bases B) adding 1 base C) deleting 1 base or adding 1 base D) deleting 1 base or adding 3 bases E) deleting 1 base or adding 2 bases

Answer 1

A reversion mutation is a mutation that reverses the effect of a prior mutation. In the case of a frame-shift mutation, which is caused by the addition of one nucleotide base, a reversion mutation would be the deletion of one base or the addition of one base. The other choices (deleting 2 bases, adding 3 bases, or deleting 1 base or adding 2 bases) are not valid reversion mutations for this type of mutation, and thus cannot be classified as such.

Frame-shift mutations occur when one or more nucleotide bases are inserted or deleted from a sequence of DNA. These mutations can cause a shift in the reading frame of the gene, resulting in a completely different amino acid sequence and a different phenotype. Reversion mutations, on the other hand, revert the effects of prior mutations, thereby restoring the normal reading frame of the gene and thus its original phenotype.