Question

In Section 12.3, "Laws of Inheritance," an example of epistasis was given for the summer squash. Cross white WwYy heterozygotes to prove the phenotypic ratio of 12 white:3 yellow:1 green that was given in the .

a) True
b) False

Answer 1

Crossing white heterozygotes (WwYy x WwYy) for summer squash demonstrates the 12 white:3 yellow:1 green phenotypic ratio due to the W gene's epistasis over the Y gene.

Step-by-step explanation:

Crossing white heterozygotes (WwYy x WwYy) for summer squash demonstrates the 12 white:3 yellow:1 green phenotypic ratio due to the W gene's epistasis over the Y gene. The example of epistasis given in the text for summer squash can be validated through a cross of white heterozygotes (WwYy x WwYy). When these heterozygotes are crossed, they demonstrate a phenotypic ratio of 12 white, 3 yellow, and 1 green offspring. This occurs because the W gene exhibits epistasis, where it masks the expression of the Y gene.

If the W gene is present in a dominant form (W-), the squash will be white regardless of the Y alleles. If the W gene is homozygous recessive (ww), then the color will depend on the Y gene: yellow if Y is present (Yy or YY), and green if homozygous recessive for the Y gene (yy). The wwyy genotype produces the green color, showing both genes in their recessive form.