Which role do genes on the Y chromosome play in testis development?

In human embryology, the development of the testis is directly governed by the presence of specific genes located on the Y chromosome.12

During early fetal development, all embryos possess undifferentiated, or indeterminate, gonads that have the potential to become either testes or ovaries. The genes on the Y chromosome act as the critical trigger that directs these primitive gonads to develop specifically as testes.21

Once the testes are formed, they begin to influence further sexual differentiation. For instance, the Sertoli cells within the developing testes secrete Müllerian inhibiting hormone, which causes the female-precursor ducts to atrophy, while the production of testosterone stimulates the development of the male genital tract. Without the influence of these Y-linked genes, the default pathway for the developing embryo is toward the female direction.2