Sex and Sexual Differentiation

Abstract

The sexual phenotype, or gender, of vertebrates is determined through either one of two main mechanisms. In most forms, it is determined by genetic factors such as the presence of certain genes that reside on particular combinations of specialized chromosomes. In others, maleness or femaleness is not as clearly rooted in genotype and is acquired independently of chromosomal composition. The sexual phenotype of such forms is under epigenetic control and is the result of environmental influences that act on the genes and regulatory mechanisms involved in sexual differentiation. Many species have evolved ways of taking advantage of this epigenetic nature of sexual differentiation. In a few species, individuals are even capable of switching from one gender to another according to the environmental conditions that they encounter.

“ . . .for strange effects and extraordinary combinations we must go to life itself, which is always far more daring than any effort of the imagination.” - Sir Arthur Conan Doyle