Describe dominant epistasis with an example.

Explanation

Dominant epistatis is a type of gene interation in which two alleles of one locus interfere or suppress the phenotypic expression of a different pair oif alleles of another gene is known as epistatic gene and the gene that is suppressed is called as hypostatic gene. When both genes are present together the phenotype is decided by the epistatic gene and not by the hypostatic gene.
In the summer squash, the white colour of the fruit is due to a dominant allele .W. and the coloured fruit is due to recessive allele .w.. In another locus hypostatic allele .G. is for yellow fruit and green fruit is due to the recessive allele .g.. When the plant with genotype WWgg is crossed while plant with genotype wwGG for yellow fruit, the `F_(1)` plants have white fruit and are heterozygous (WwGg). When `F_(1)` are selfed, they give rise to `F_(2)` with phenotype ratio of 12 white: 3 yellow :1 green

Phenotype: White 12: Yellow 3: Green 1
Since W is epistatic to the allele .G. and .g., the white which is dominant masks the effect of yellow or green.