What is the main difference between dominance and epistasis as described in the source?

What is the main difference between dominance and epistasis as described in the source?

• A. Dominance is a gene affecting another gene on the same loci and different chromosomes, while epistasis is a gene affecting another gene on a different locus on the same chromosome.
• B. Dominance affects multiple traits, epistasis affects a single trait
• C. Dominance occurs only in homozygotes, epistasis only in heterozygotes
• D. Dominance relates to environment, epistasis to genetics

Answer: (C)

Dominance and epistasis differ in the level at which gene interactions occur. Dominance describes how alleles at a single locus interact in a heterozygote: one allele may mask the other, so the phenotype resembles one of the homozygous forms. This can be complete, incomplete, or co-dominant, depending on how the alleles express in Aa individuals. Epistasis involves genes at different loci. The product of one gene can mask or modify the expression of a gene at another locus, altering the phenotype in a way that depends on the combination of genotypes across these loci. A classic example is Labrador coat color, where one gene controls pigment production and another controls pigment deposition; certain alleles at the second locus can mask the effects of the first, leading to colors that wouldn’t appear from the first gene alone. So, the main difference is single-locus allele interactions in dominance versus interlocus gene interactions in epistasis.

Dominance and epistasis differ in the level at which gene interactions occur. Dominance describes how alleles at a single locus interact in a heterozygote: one allele may mask the other, so the phenotype resembles one of the homozygous forms. This can be complete, incomplete, or co-dominant, depending on how the alleles express in Aa individuals.

Epistasis involves genes at different loci. The product of one gene can mask or modify the expression of a gene at another locus, altering the phenotype in a way that depends on the combination of genotypes across these loci. A classic example is Labrador coat color, where one gene controls pigment production and another controls pigment deposition; certain alleles at the second locus can mask the effects of the first, leading to colors that wouldn’t appear from the first gene alone.

So, the main difference is single-locus allele interactions in dominance versus interlocus gene interactions in epistasis.