Q21: The reason for deviation from Mendel's dihybrid cross ratio in... - Genetics and Evolution - Biology CUET UG 23-08-2022 Shift 2 Paper | Agrigyan

When T.H. Morgan and his group carried out dihybrid crosses in Drosophila to study genes that were sex-linked, the $F_2$ phenotypic ratios deviated very significantly from the 9:3:3:1 ratio predicted by Mendel's law of independent assortment. Morgan attributed this to the physical association or linkage of the two genes on the same chromosome.