Question

Epistasis differs from dominance because

• A. In epistasis one gene pair masks the expression of another pair of genes.
• B. Epistasis is an allelic interaction.
• C. Many genes collectively controls a particular phenotype.
• D. One gene pair independently controls a particular phenotype.

Answer 1

The correct option is A In epistasis one gene pair masks the expression of another pair of genes.

In epistasis, one gene pair mask the expression of another pair of genes. Epistatic gene is a gene that determines whether or not a trait will be expressed. The system of genes that determines skin colour in man, for example, is independent of the gene responsible for albinism (lack of pigment) or the development of skin colour. This gene is an epistatic gene. When the albino condition occurs, the genes that determine skin colour are present but not expressed. Dominance is greater influence by one of a pair of genes (alleles) that affect the same inherited character. If an individual pea plant with the alleles T and t (T = tallness, t = shortness) is of the same height as a TT individual, the T allele (and the trait of tallness) is said to be completely dominant; if the Tt individual is shorter than the TT but still taller than the tt individual, T is said to be partially or incompletely dominant; i.e., it has a greater influence than t but does not completely mask the presence of t, which is said to be recessive.

Thus, the correct answer is option A.