Graves J A, Schmidt M M
Department of Genetics and Human Variation, La Trobe University, Melbourne, Australia.
Curr Opin Genet Dev. 1992 Dec;2(6):890-901. doi: 10.1016/s0959-437x(05)80112-1.
Mammalian sex chromosomes evolved (and are still evolving) from a homomorphic pair by the progressive loss of active genes from the Y chromosome. Among the changes that have accompanied this differentiation, it is difficult to determine causes, effects and correlates. Comparative studies suggest that the choice of a gene, and thus a chromosome pair, to control the sex-determining pathway may be quite arbitrary, and that sex chromosomes and sex-determining genes are more likely to be the products of random changes than the products of selection for function.
