Beginner's guide to genetics: Sex and genetics
In the third part of our series, Adrián J González and colleagues explain the genetic bases of sexual development
- By: Adrián J González, Luis R Macias, Regina Gómez-Palacio, Osvaldo M Mutchinick
Throughout history, humans have tried to discover differences between men and women, and how this determines the nature of sex. In the last century, scientists began to unlock the molecular and genetic mechanisms of sexual development. This process has not been so simple, however; sexual development consists of an orchestrated, ordered, and interrelated cascade of events.
The first step is the establishment of genetic sex (XX or XY). This results when a spermatozoid with an X or Y chromosome (genetic sex) fertilises an oocite, which carries an X chromosome. The second step is development of sex gonads. At the beginning of this step, regardless of genetic sex, embryos develop a bipotential primordium--a structure in the forming embryo that can turn into female or male gonad. This then differentiates to form the testis in XY embryos or the ovary in XX embryos, thereby defining gonadal sex. The last step is phenotypical