Practice question

Gene interaction refers to cooperative or antagonistic action of alleles at two or more non-allelic loci together determining expression of single trait, deviating from one gene-one trait model. Pathway may require sequential enzymes, regulatory proteins, structural components where variant at any locus alters final phenotype. Resulting F2 ratios modify classic 9:3:3:1 into epistatic forms 9:7, 12:3:1, 15:1, 13:3, indicating biochemical interdependence. Examples include comb shape in chickens, coat color mammals, fruit morphology. Concept reveals integration of developmental pathways beyond simple Mendelian inheritance, emphasizing networks rather than isolated genes.