Many of the color varieties of summer squash are determined

Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Crosses among heterozygotes give a 12:3:1 ratio. What type of gene interaction would account for these results?

Solution

The type of gene interaction that would account for these results is Dominant epistatis.

Explanation :Let the dominant alleles be A and B but when ‘A’ masks the expression of ‘B’ ‘A’ is called the epistatic gene of ‘B’. \'A\' expresses itself only in the presence of ‘B’ or b allele.So,it is referred as dominant epistasis. B will express only when ‘aa’ is present. So,in the 9: 3: 3: 1 ratio both 9 and 3 will express the ‘A’ gene and the ratio will change to 12: 3: 1.