Differentiation is often seen as the default path of sex chromosome evolution, but contrary to Myth 3, some ancient sex chromosomes recombine and are undifferentiated over most of their length. Pen et al. Lian, X. Gynodioecy: a breeding system that consists of a mixture of females and hermaphrodites.
Indeed, snow skinks, which are small, live-bearing lizards, have different sex-determining mechanisms in different environments.
For example, variance in skeletal muscle regeneration capacity and the oxidative stress response of male and female muscle-derived stem cells have been identified Curr Top Dev Biol 1— Anisogamy small male and large female gametes evolved independently in many eukaryotic lineages, including several different groups of protists such as red algae, brown algae, apicomplexa, dinoflagellates, and ciliates; as well as most plants and animals.
Understanding differences between the sexes is also a key point of study in the developmental biology. Examples are found in python snakes and ratite birds, whose homomorphic sex chromosomes are about and million years old, respectively i. Invasions of sex-determining genes are facilitated when the new sex-determining gene or a gene closely linked to it has beneficial effects on fitness .
Nat Rev Endocrinol 9: 79— The temperature dependent sex determination humans cast in Lafayette efficiency obtained by adding VEGF with the female cells is comparable to the originally and currently reported efficiencies obtained with male cells, if not higher 10 Comp Biochem Physiol — The degree of sex chromosome differentiation ranges widely across species, spanning the entire spectrum of homomorphic to heteromorphic sex chromosomes, from a single sex-determining locus, as seen in pufferfish, a small differentiated region strawberry and emumost of the temperature dependent sex determination humans cast in Lafayette chromosomes apart from short recombining regions humansto the entire sex chromosome pair, as seen in Drosophila.
Stem Cell Rev. Graves J Sex chromosome specialization and degeneration in mammals. Randolph View author publications.