ABSTRACT
Sex determination, the process involved in establishing the gender of an organism, is a simple binary fate decision: male or female (Penman and Piferrer, 2008). Sex determination mechanisms are responsible for producing the sex ratio, a critical demographic parameter for population viability (Opsina-Alvarez and Piferrer, 2008). The two major types of sex-determining mechanisms are: genotypic sex determination (GSD), where the sex is determined at fertilization, and environmental sex determination (ESD), where sex is determined by environmental cues after fertilization. These mechanisms commit the morphologically undifferentiated bipotential gonad primordium, not yet determined, to a gonadal rudiment (ovary or testis fate). Sex differentiation is the process that transforms those determined and undifferentiated rudiments into ovaries or testes. Embryonic gonads represent the unique organ primordium that could develop into two different adult tissues. Sexual fate is accomplished by activating the ovarian or testicular pathway and at the same time repressing the alternative differentiation cascade (Gilbert, 2013). In this context, activation or suppression of a variety of genes in a strict spatiotemporal dimension is needed; epigenetic mechanisms for the
CONTENTS
5.1 Introduction ............................................................................................................................ 75 5.2 Sex Determination in Austrolebias charrua ..........................................................................77
