Of the following statements which is/are correct?
(A) During incomplete dominance, modified allele is the dominant allele
(B) In polygenic inheritance, the effect of each allele is additive
(C) A gene is called pleiotropic when it exhibit multiple phenotypic expression
(D) Mutation means alteration of DNA sequence which ensures change only in the phenotype of an organism
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) and (C) only
(A) During incomplete dominance, modified allele is the dominant allele — False. In incomplete dominance neither allele is dominant; the F1 shows an in-between phenotype (pink flowers of snapdragon from red × white). In ordinary dominance it is the unmodified (normal) allele that is dominant, and the modified allele is usually recessive.
(B) In polygenic inheritance, the effect of each allele is additive — True. A polygenic trait, such as human skin colour, is controlled by three or more genes. The phenotype reflects the contribution of each allele, so their effects add up.
(C) A gene is called pleiotropic when it exhibit multiple phenotypic expression — True. A pleiotropic gene is a single gene that affects many phenotypic traits. In phenylketonuria, one mutated gene causes mental retardation and also reduced hair and skin pigmentation.
(D) Mutation means alteration of DNA sequence which ensures change only in the phenotype of an organism — False. A mutation alters the DNA, so it changes the genotype first. The phenotype may or may not change as a result. The word “only” makes the statement wrong.