Answer:
SRY
Step-by-step explanation:
Sex determination in mammals including humans is genetically and hormonally controlled.
Genetically gonadal sex determination is mediated by a gene called SRY. This gene is known as the mammalian Y-chromosomal testis-determining gene. It induces sex determination in males.
Recent studies revealed that SRY plays an important role in inducing Sertoli cells differentiation. The Sertoli cells, in turn, guide testis formation.
Therefore, in males, differentiation of testis is switched on by expression of the Y-linked SRY gene.