Question

Squash color is an example of dominant epistasis. Plants with at least one W allele produce white squash, regardless of the alleles at the Y/y locus (yy = green, Y = yellow). What is the percentage of white squash plants obtained from a cross between a green squash plant and a yellow squash plant?

Answer 1

From a cross between a green squash (wwyy) and a yellow squash (wwYY or wwYy), white squash cannot be produced, as neither parent has the dominant W allele necessary for white coloration due to dominant epistasis.

Step-by-step explanation:

The percentage of white squash in the offspring from a cross between a green squash plant and a yellow squash plant, which is an example of dominant epistasis, can be calculated based on the rules of Mendelian genetics. In this scenario, the green squash plant is homozygous recessive (wwyy) and the yellow squash is either YY or Yy but must be ww to display yellow color. To produce white offspring, at least one parent must have a dominant W allele, which neither of these parents has (as one is green and the other is yellow). Therefore, it is not possible to produce white squash from the cross described. If this were a cross of two WwYy heterozygotes, then the ratio would be 12 white:3 yellow:1 green, as 12 offspring would have at least one dominant W allele, masking the color given by the Y gene.