THE MOLECULAR-BIOLOGY OF TEMPERATURE-DEPENDENT SEX DETERMINATION

Many reptiles do not have heteromorphic sex chromosomes and for these species sex is determined during embryogenesis by the temperature of e gg incubation rather than at conception. The phenomenon of temperature -dependent sex determination (TSD) was discovered almost thirty years ago, but few advances have been made towards the elucidation of its me chanism. In the past few years substantial progress has been made in t he understanding of the molecular basis of XY chromosomal (genetic) se x determination (GSD) through the discovery of SRY. It is now possible to start comparing TSD with GSD. TSD is found in some evolutionarily ancient vertebrates and has been postulated to be the ancestral proces s from which GSD has evolved. If this is true then the two mechanisms may share a common molecular basis. This paper details the current kno wledge of TSD, our progress on the investigation of the involvement of SRY-type proteins, and finally presents some of the problems that nee d to be resolved to gain an understanding of the molecular basis of TS D.