Question

Out of two alleles of the same gene, one finds morphological expression. The phenomenon is

• A. Epistasis
• B. Codominance
• C. Dominance
• D. Incomplete dominance

Answer 1

Answer: (C)

Dominance

Epistasis is the non-allelic gene interaction where the presence of one gene masks the expression of another gene; it is an attribute of polygenic trait while the question is about two alleles of the single gene; option A is wrong. When both recessive and dominant traits are expressed in a heterozygous genotype; it is codominance; but here only one allele show its presence in heterozygous genotype, option B is incorrect.

As we know that, a trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in the heterozygous individual is called as a dominant trait and the phenomenon is called dominance. The other factor whose effect is masked by the presence of dominant factor is called recessive factor. This makes option C correct. Incomplete dominance is the condition when none of the factors of a gene is dominant and the phenotype of the heterozygous dominant individual is a blend of dominant and recessive traits. But here the one allele is expressed in heterozygous genotype which makes option D wrong.