Question

The phenomenon of a single gene regulating several phenotypes is called as

• A. Multiple allelism
• B. Epistasis
• C. Incomplete dominance
• D. Pleiotropism

Answer 1

The correct option is D Pleiotropism

Epistasis is the non-allelic gene interaction where the presence of one gene masks or alters the expression of another gene thereby not allowing the later one to express fully. Coat colour in mouse and fruit colour in squash are the examples of epistasis.

Pleiotropy is the condition where a gene has its own independent effect but also modifies the expression of a completely different gene quantitatively. For example, gene governing wing shape affects the number of facets of bar-eyed Drosophila. When both recessive and dominant traits are expressed in a heterozygous genotype, it is codominance.

Incomplete dominance is the condition when none of the factors of a gene is dominant, the phenotype of the heterozygous dominant individual is a blend of dominant and recessive traits.

Multiple allelism is the condition where a trait is controlled by more than two alleles of a gene, for example, human blood group is governed by single gene "I" which has three alleles; I${}^A$, I${}^B$ and I${}^O$.

The correct answer is option D.