Question

Suppose two independently assorting genes are involved in the pathway that determine fruit color in squash. These genes interact with each other to produce the squash colors seen in the grocery store.At the first locus, the W allele codes for a dominant white phenotype, whereas the w allele codes for colored squash. AT the second locus, the allele Y codes for a doinant yellow phenotype, and the allele codes for a recessive green phentoype. The phenotypes from the first locus will always maske the phenotype produced by the second locus if the dominant allele (W) is present at the first locus. This masking pattern is known as dominant epistasis.A dihybrid squash, WwYy, is selfed and produces 180 offspring. How many offspring are expected to have eachof the following phenotypes?

Answer 1

The phenomenon in which the dominant allele of one gene overshadows the expression of all the alleles of another gene is termed as dominant epistasis. The segregation ratio obtained in dominant epistasis is 12: 3: 1. Thus, there are 16 combinations in total, of which 12 will be white, 3 yellow and one will be exhibiting green phenotype.

It is given that a dihybrid squash is selfed and generates 180 offspring. Thus, the offspring exhibiting white phenotype will be 180 * 12/16 = 135

The offspring exhibiting yellow phenotype will be 180*3/16 = 34

The offspring exhibiting green phenotype will be 180*1/16 = 11