Sex-linked cross in Drosophila
Unlike the case with autosomal loci, the reciprocal cross of a red-eyed male fly to a white-eyed female produces a different result. In the F1 generation, all of the females are red-eyed, and all of the males are white-eyed. Because this is the exact opposite of the P generation, this is refered to as "criss-cross" inheritance. In the F2 generation, there is a 1:1:1:1 ratio of the four possible combinations of sex and eye colour.