Epistasis is when a gene overrides the effects of another ge

Epistasis is when a gene overrides the effects of another gene. What type of epistasis is present in the following pathway? Which is epistatic, the dominant or the recessive allele?

Solution

Epistasis or gene masking is a molecular phenomenon in which presence of a dominant or recessive gene/allele of different/same function masks the phenotype of the other gene/allele even when the other gene is present in dominant manner. This phenomenon is responsible for generation of un-expected phenotypes in the organisms even when they are genotypically normal. Under epistasis, the organisms deviate from normal Mendelian pattern of inheritance and hence, show deviation in genotypic and phenotypic ratios in double as well as multiple gene-related characters.

According to the question, it can be clearly observed that the gene for green and yellow pigements are under epistatic conditions. Here, it must be carefully observed that the dominant allele for C masks the presence of any type of green pigment color i.e. dominant G or recessive g. Thus, this represents a clear example of dominant epistasis.

Resultantly, the presnce of any dominant allele in homozygous or heterozygous condition for gene for yellow pigment will always mask the gene for green pigment. Also, for a plant to produce green pigment, the genotype of the yellow pigment should be homozygous recessive in nature.

This explains that the present example deciphers dominant epistasis.