Practice question

Epistasis describes functional masking where genotype at one locus alters phenotypic expression of another non-allelic locus without changing meiotic segregation behaviour itself. Monohybrid 3:1 ratios persist because alleles still separate at anaphase, yet combinational phenotypes collapse when biochemical steps interact in same pathway. Dihybrid expectation 9:3:3:1 therefore becomes modified into variants like dominant 12:3:1, complementary 9:7, duplicate 15:1 or recessive 9:3:4 depending on whether inhibitor, redundant or cooperative enzymes are involved. Hence alteration of dihybrid ratio serves as diagnostic signature of epistatic interaction.