Question

Sol.(b) [Key Concept: Dominant Epistasis — Squash Fruit Colour] Fruit colour in Summer Squash (Cucurbita pepo) is an example of DOMINANT EPISTASIS. A dominant epistatic allele (W) suppresses the phenotypic expression of a non-allelic gene (Y for yellow, yy for green), regardless of whether the latter is dominant or recessive. WW or Ww → white fruit (W epistatic over Y/y); wwY_ → yellow; wwyy → green. The F2 ratio is 12:3:1 (white:yellow:green). W is dominant and epistatic to the Y gene.