Question

Two animals with dark fur are crossed multiple times, and, after analyzing all of their offspring, the following numbers emerge: 71 dark, 47 grey, 8 white. Explain:

- what kind of inheritance is this?

- show the genotypes of the parents

- show the genotypes for all three phenotypes of the offspring

Answer 1

Answer:

The total number of individuals = 126

The proportion of dark fur phenotype = 71/126 = 0.56

The proportion of grey fur phenotype = 47/126 = 0.37

The proportion of white fur phenotype = 8/126 = 0.06

The type of interaction is Duplicate interaction. The digenic epistatic ratio is 9:6:1. If the dominant alleles of both the gene are present (in either homozygous or heterozygous form) the phenotype is dark fur. If dominant allele (in either homozygous or heterozygous form) any one gene is present the phenotype is grey fur. If there is no dominant allele of any of the two genes, the phenotype is white fur.

The genotypes of the parent are heterozygous since they produce three different phenotypes. The genotype of the dark fur is Aa Bb.

The genotypes for all three phenotypes of the offspring are,

Black fur – A_ B_ (the dashed place can be taken up by a dominant or a recessive allele of the corresponding genes. In these alternatives the resulting phenotype (i.e., the black fur) will not change.)

Grey fur – A_ bb, aa B_ (the dashed place can be taken up by a dominant or a recessive allele of the corresponding genes. In these alternatives the resulting phenotype (i.e., the grey fur) will not change.)

White fur – aa bb