Q.The dominant epistasis ratio is

Step 1. Dominant epistasis occurs when a dominant allele at one locus masks the phenotypic expression of a different locus entirely, as seen in summer squash fruit colour (dominant W masking the yellow/green G locus).

Step 2. Of the 16 F2 combinations from a standard dihybrid self-cross, the 12 combinations carrying at least one dominant W allele are all masked to the same (white) phenotype, while the remaining 4 combinations (all homozygous ww) split further, by the G locus, into 3 yellow and 1 green. …

Recall the specific 12:3:1 ratio associated with dominant epistasis (12 masked …

• Confusing the dominant epistasis ratio (12:3:1) with the standard dihybrid ratio (9:3:3:1). …