Give an account of sex linkage in Drosophila and man.

Explanation

Sex linkage is the phenotypic expression of an allele related to the allosome of the individual. In autosomal chromosomes both sexes have the same probability of existing but since humans have many more genes on the female X-chromosome than on the male Y-chromosome, these are much more common than Y-linked traits. Examples of sex-linked traits in humans are haemophilia and colour blindness . Thomas Hunt Morgan discovered sex linkage in fruitfly. It supported the chromosomal theory of heredity. Morgan proposed that the inheritance of eye colour is related to the sex of the offspring. He found that the gene for eye colour is located on X-chromosome. There is no corresponding allele for this trait on Y-chromosome. Example During the cross between white-eyed male and red-eyed female, the F -flies (both male and female) were all red-eyed indicating that white eye colour is recessive to the normal red eye colour.