Solution:
A dominant epistatic allele suppresses the expression of a non-allelic gene whether the latter is dominant or recessive. The gene which suppresses the expression of a nonallelic gene is known as epistatic gene. The gene or locus which is suppressed by the presence of nonallelic gene is termed as hypostatic gene. In summer squash or Cucurhita pepo, there are three types of fruit colour' yellow, green and white. White colour is dominant over other colours while yellow is dominant over green. Yellow colour is formed only when the dominant epistatic gene is represented by its recessive allele (w). When the hypostatic gene is also recessive (y), the colour of the fruit is green,
