Extinct and Extant Reptiles: A Model System for the Study of Sex Chromosome Evolution

The evolution and functional dynamics of sex chromosomes are focuses of current biological research. Although common organismal morphologies and functions of males and females are found among amniotes, underlying sex chromosome organizations and sex-determining mechanisms are widely variable. This chapter investigates the role that reptiles play in the study of sex chromosome evolution. Reptile studies have described the coevolution of genotypic sex determination and viviparity, the adaptive significance of sex-determining mechanisms, and shared ancestry of chromosomes. Novel resources, including whole-genome sequences and mapped sex-linked markers, have allowed researchers to examine sex chromosome evolution in reptiles, an important group for this type of study for their position as the sister group to mammals. Compared with mammals, reptiles exhibit much more variability in sex chromosome organization, providing raw material for study of sex chromosome evolution across amniotes.