Lee B. Smith • Rod T. Mitchell
Iain J. McEwan

2013

Is it a boy or a girl? That is the first question all new parents are asked on the arrival of a new baby. Whilst it could be argued that there is little other information that could be requested on the birth of a child, this neatly highlights the significance of gender, which will impact on the remainder of the child’s life, including risk of specific disease and ultimately life expectancy. The sex of the fetus is defined by the inheritance or not of a single gene, SRY, which is located on the Y chromosome. This gene is activated during fetal life to define Sertoli cells that drive the undifferentiated gonad towards a testicular fate.