Final answer:
A reversion mutation, also known as a back mutation, is a change in the DNA that restores a mutant allele to the wild-type form.Option A is the correct answer.
Step-by-step explanation:
A mutation is a heritable change in the DNA sequence of an organism, potentially affecting the organism's phenotype. When discussing mutations, we categorize them in different ways based on their effects on the DNA sequence and the resulting phenotype.
A particular kind of mutation that has drawn attention is one that reverses the effect of a previous mutation, restoring the original DNA sequence and phenotype.
This is known as a back mutation or a reversion mutation. Back mutation is significant because it implies that the changes in the DNA leading to a mutant phenotype can be undone, essentially 'going back' to the wild-type or original state. Given these details, the answer to the student's question is: A reversion mutation is one that converts a mutant allele back to the wild-type form.