Question

A recessive mutant allele of an autosome gene in a species of mouse results in a shorted tail in males when homozygous. However, when homozygous in females, this genotype has no effect, and the mice have normal tails. What is this genetic phenomenon called?

Answer 1

The phenomenon is called sex-limited inheritance. It is different from sex-linked inheritance and epistasis, which is when one gene masks the expression of another gene, as in the case of mouse pigmentation.

Step-by-step explanation:

The genetic phenomenon where a recessive mutant allele of an autosome gene results in a trait in one sex but not the other is known as sex-limited inheritance. In the case described, the mutant allele leads to a short tail in homozygous males but has no effect when homozygous in females.

This type of inheritance is distinct from sex-linked inheritance, where traits are associated with genes found on sex chromosomes, and also from epistasis, where one gene's expression is affected by the presence of one or more 'modifier genes'.

Epistasis is illustrated in mice pigmentation, where the presence of homozygous recessive alleles at the C locus (cc) leads to albinism, regardless of the genotype at the A locus, thus the C gene is epistatic to the A gene.