Question

Match the genetic phenomena with their respective ratios.

	List I		List II
A	Inhibitory gene ratio	1	9:3:4
B	Complementary gene ratio	2	1:1:1:1
C	Recessive epistasis ratio	3	12:3:1
D	Dihybrid test cross ratio	4	9:7
E	Dominant epistasis ratio	5	13:3

A. a - 5, b- 4, c- 3, d- 2, e- 1
B. a- 4, b- 5, c- 1, d- 2, e- 3
C. a-1, b- 2, c- 4, d- 3, e- 5
D. a- 2, b- 1, c- 4, d- 5, e- 3
E. a- 5, b- 4, c- 1, d- 2, e- 3

Answer 1

Hint: In genetics, basically there are two variants which are dominant, and recessive. Dominant variant always masks the other variant of the same gene.

Complete answer:
> Inhibitory gene ratio: It is also called as suppressor genes which suppress or inhibit the action of mutation of another gene which finally results in the normal phenotype.

> Complementary gene ratio: For complementary gene ratio, both dominant alleles of both genes are to be expressed for the given phenotype, where the ratio is 9:7, which means 9 have at least one set of dominant alleles, 7 have either no dominant alleles.

> Recessive epistasis ratio: Here mainly the recessive allele of the gene masks the dominant allele, where the ratio is usually 9:3:1.

> Dihybrid test cross ratio: here the alleles are assorting their ratio independently. The ratio of 1:1:1:1 is the test cross of the dihybrid. Whereas the self ratio of the dihybrid is 9:3:3:1.

> Dominant epistasis ratio: here the mutation occurs by the expression of alleles which is done by suppressing the expression of other alleles of another gene and the ratio is 12:3:1.

So the order is inhibitory gene ratio is - 13:3
Complementary gene ratio - 9:7
Recessive epistasis ratio - 9:3:4
Dihybrid test cross ratio - 1:1:1:1
Dominant epistasis ratio - 12:3:1

Hence, The correct option is E. a-5, b-4, c-1, d-2, e-3

Additional information: Offspring distribution pattern according to the genotype is said to be genotypic ratio, where based on this ratio the phenotype is determined, and it is nothing but, number of times, genotype would appear in the offspring after the test cross.

Note: One should mainly understand about the terms of dominant and recessive nature of the gene, so that all the ratio definitions can be easily understood which helps to remember the ratios by explanation of definition.