Question

A mutant allele can exert its dominance over a wild-type allele by which of the following changes?

1) Mutation in the promoter region of the mutant allele
2) Mutation in the coding sequence of the mutant allele
3) Mutation in the enhancer region of the wild-type allele
4) Mutation in the intron region of the wild-type allele

Answer 1

A mutant allele can dominate over a wild-type allele through mutations that affect the amount or function of the produced protein, often by alterations in the promoter or coding sequence that influence gene transcription and protein product.

Step-by-step explanation:

A mutant allele can exert its dominance over a wild-type allele by causing an alteration in the genetic message. This can be through a mutation in the promoter region of the mutant allele, which could increase or decrease the rate of transcription and ultimately the amount of protein produced. A mutation in the coding sequence of the mutant allele can result in a changed protein product that could be overactive or mislocalized. These changes might enhance the function of the wild-type gene product or change its distribution in the body, leading to observable mutant phenotypes even in the presence of a wild-type allele.

For example, the Antennapedia mutation in Drosophila results in an expanded distribution of the gene product, causing legs to develop on the head in place of the antennae. Similarly, mutations can lead to the production of a constitutively activated protein in the case of oncogenes, overriding the functionality of the wild-type allele.