Question

In a dihybrid cross, when one pair of alleles show incomplete dominance, genotypic ratio comes to
(a) 3:6:1:2:1
(b) 1:2:2:4:1:2:1:2:1
(c) 9:3:3:1
(d) 1:2:1

Answer 1

Hint: Dihybrid cross is a cross between two different genes that vary in two observable traits. Incomplete dominance is described as a type of intermediate inheritance in which one allele for a specific character is not exhibited fully over its paired allele.

Complete answer:
Incomplete dominance takes place because none of the two alleles is completely dominant over the other. This results in a phenotype that is a combination of both. The effect of complete or incomplete dominance is exhibited in the phenotype of the organism, the genotype remains unchanged through this. Therefore, the genotypic ratio of a dihybrid cross would always remain the same, i.e., 1:2:2:4:1:2:1:2:1.
Incomplete dominance is the situation when none of the alleles of a gene is dominant, the phenotype of a heterozygous dominant individual is a mix of dominant and recessive traits. At this moment, a monohybrid cross between two pure varieties gives a 1:2:1 phenotypic ratio in ${F}_{2}$ generation. The phenotypic ratio of ${F}_{2}$ generation of a dihybrid cross is 9:3:3:1 administered that the alleles of both follow a dominant-recessive relationship. When alleles of one gene follow a dominant and recessive relationship but the alleles of the second gene are codominant, the ${F}_{2}$ phenotypic ratio of a dihybrid cross becomes 3:6:1:2:1.

So, the correct answer is ‘1:2:2:4:1:2:1:2:1’.

Note:
-Gregor Mendel is well known as the father of modern genetics. He was awarded this honor for his experiments which set the base work for genetics and inheritance.
-The child of parents each with curly hair and straight hair will every time have wavy hair. Carriers of Tay-Sachs disease exhibit incomplete dominance.
-The Andalusian chicken exhibits incomplete dominance on its feather color.