Question

Fruit colour in squash is an example of
A. Recessive epistasis
B. Dominant epistasis
C. Complementary genes
D. Inhibitory genes

Answer 1

Hint: The fruit colour refers to the phenotype trait. Depending upon the mutation of the gene, the phenotype of an individual is decided. A fruit colour is a form of non-Mendelian inheritance in which one gene is capable of interfering with the expression of another.

Complete answer: In genetics, the phenomenon in which the effect of gene mutation is dependent on the absence or presence of mutations in one or more genes is called epistasis. These genes are called modifier genes as they modify the genetic information by mutation. A mutation refers to the alteration of the nucleotide sequence of the DNA. The genetic background, in which the mutations occur determines the effect of the mutation. In epistasis, the phenotype of one gene’s allele is masked by the other gene’s allele. Different types of epistasis are recessive epistasis and dominant epistasis. In recessive epistasis, the recessive allele of one gene masks the effect of the other allele of a gene. Phenotypic ratio of recessive epistasis in F2 is 9:3:4. The progeny produced shows incomplete dominance. In dominant epistasis, the dominant allele of one gene masks the effect of the allele of another gene. The phenotypic ratio of dominant epistasis is 12:3:1. Example of dominant epistasis is the colour of the summer squash fruit.
So, option B is the correct answer.

Note: The phenotype is not necessarily dependent on the genotype of an organism. The phenotype of an individual depends on the expression of the genotype. Expressivity is the intensity with which a particular genotype is expressed.