Question

Recessive epistasis is shown by-
A) Flower colour in sweet pea
B) Fruit colour of summer squash
C) Coat colour of mice
D) Shape of comb in poultry

Answer 1

Hint:To answer this question, we must learn about epistasis, its types and other gene interactions. Epistasis is a genetic phenomenon where one gene masks the expression of another gene, mostly present on another locus.

Complete answer:
Epistasis is a genetic phenomenon where the effect of a gene mutation depends on the presence or absence of mutations in one or more different genes which are called modifier genes. There are different types of epistasis-
>Dominant epistasis- When the expression of both dominant and recessive alleles is masked by a dominant allele from another locus, it is called as dominant epistasis. Its ratio - 12:3:1.
>Dominant inhibitory epistasis- when a gene suppresses the expression of another gene.
>Duplicate dominant epistasis- when a dominant allele masks recessive genes at 2 locations. Ratio- 15:1
>Duplicate recessive epistasis- when recessive allele masks expression of dominant gene at 2 places. Ratio- 9:7
>Polymeric gene interaction epistasis
>Recessive epistasis- a recessive allele masks the expression of other genes. Ratio- 9:4:3
Recessive epistasis in mice
Recessive epistasis- And recessive epistasis, one gene is recessive, it is masked by a dominant gene; it can only express itself if there are two copies of the recessive allele. Thus, we need two copies of the recessive allele to override other dominant genes. An example of it is the coat colour of Labradors, they can have one of three main colours: black, brown or yellow, also the coat colour of mice which can be agouti, black or albino.

The correct answer is- C. Coat colour of mice

Note:Expression of one gene is affected by expression of other inherited genes.Coat colour of mice is one of the major recessive epistasis. Others are examples of complementary genes, polymeric genes and lethal genes.