Epistasis occurs when one gene's allele masks another gene's effect. Which example best illustrates this?

Epistasis occurs when one gene's allele masks another gene's effect. Which example best illustrates this?

• A. Coat color where one gene masks expression of another (epistatic white/yellow phenotype)
• B. Two genes additively influence a trait
• C. A mutation causes a frameshift
• D. A gene duplication increases gene dosage

Answer: (A)

Epistasis is when a gene at one locus masks or overrides the effect of a gene at another locus, so the visible trait depends on the combination of genes rather than a simple, additive effect. The coat color example fits this best: an epistatic gene that blocks pigment production can produce a white or yellow phenotype regardless of what alleles the second gene has that would normally determine color. This masking across genes is the hallmark of epistasis. In contrast, additive gene action sums effects from two genes without masking, a frameshift mutation is a change within a single gene, and gene duplication affects the dosage of one gene rather than interactions between genes.

Epistasis is when a gene at one locus masks or overrides the effect of a gene at another locus, so the visible trait depends on the combination of genes rather than a simple, additive effect. The coat color example fits this best: an epistatic gene that blocks pigment production can produce a white or yellow phenotype regardless of what alleles the second gene has that would normally determine color. This masking across genes is the hallmark of epistasis. In contrast, additive gene action sums effects from two genes without masking, a frameshift mutation is a change within a single gene, and gene duplication affects the dosage of one gene rather than interactions between genes.