Question

In a dihybrid cross, the F2 ​ phenotypic ratio is 13: 3. It is a case of

a) Complementary genes

b) Epistatic genes

c) Multigenic inheritance

d) Incomplete dominance

Answer 1

Phenotypic ratio is a concept that describes the likelihood of discovering patterns and frequencies of genetic trait outcomes in organisms' offspring. A phenotype is a measurable or detectable trait that results from the expression of genes.

Complete answer:

The phenotypes were chosen from among the sixteen possible allele blends resulting from the intersection of male and female gametes, where two attributes are considered.

a) Complementary genes– Reciprocal qualities are two genes present on isolated loci that interact to establish a dominant phenotypic character; neither of them can communicate if present alone. 9:7

the proportion of descendants is gotten because of these qualities in the F2 ​ generation. It's a Mendel dihybrid proportion that's been adjusted.

b) Epistatic genes - An epistatic gene is one that covers the action of another quality, and the cycle is called epistasis. The proportion of offspring acquired due to these attributes in the F2

generation is either 9:3:4 or 12:3:1. It's a Mendel dihybrid proportion that's been adjusted.

c) Multigenic inheritance - Quantitative or polygenic inheritance refers to the inheritance of a character due to the existence of several qualities. In this case, dominant alleles have a combined effect. Polygenes are traits that are linked to this. In this case, rather than Mendel dihybrid proportion, 1:4:8:4:1 dihybrid proportion is acquired in the F2 generation. Incomplete dominance refers to the expression of new aggregates in offspring that are not the same as the parental traits.

d) Incomplete dominance results from a cross in which each parental contribution is genetically unique and gives rise to progeny whose phenotype is intermediate and therefore this option is incorrect as the phenotype is not intermediate.

Hence, the correct answer is Option (b).

Note: It’s important to remember that the law of isolation is the only one of Mendel's three proposed laws that is universally accepted and accurate. The rule of free arrangement only applies to traits that are spread over several chromosomes.