Phenotypic Femininity in Genetically Female Individuals Induced by Male-Associated Chromosomes

Turner syndrome (45X) is characterised by the absence of secondary sexual characteristics, while Klinefelter syndrome (47XXY) is marked by the presence of male sexual characteristics that are feminising. Aromatase is an enzyme that requires testosterone to be produced before it can act on it and turn it into oestrogen. Oestrogen then acts on the stem cells of the female secondary sex tissues, causing them to proliferate and develop into the characteristic features.