Morgan's sex linkage experiment, illustration

Morgan's sex linkage experiment, illustration. Punnet square showing one of the experiments performed in 1910 by US geneticist Thomas Hunt Morgan. He crossed a mutant white-eyed male fly (Drosophila melanogaster) with a red-eyed female fly to produce a generation of F1 flies. He then mated a white-eyed male (upper left) with an F1 red-eyed female fly (upper right) to obtain the F2 generation illustrated here. The X chromosome is carrying the colour trait: white (W) or red (R). The F2 males have white eyes when they inherit the mutant (white) gene on the X chromosome from their mother. F2 females only show the trait if they inherit mutant genes on both X chromosomes. This phenomenon is known as sex link inheritance, and the trait examined here is an X-linked recessive trait. This work led to Morgan being awarded the 1933 Nobel Prize in Physiology or Medicine.