A series of enzymatic steps in the testis lead to the conversion of ch
olesterol to the male sex steroid hormones, testosterone and 5alpha-di
hydrotestosterone. Mutations in any one of these steps are presumed to
alter or block the development of the male phenotype. Most of the gen
es encoding the enzymes involved in this pathway have now been cloned,
and mutations within the coding regions of these genes do, in fact, b
lock development of the male phenotype.