Final answer:
In the presence of the SRY gene, germ line cells in embryos with the Y chromosome differentiate into testes, which are essential for male reproductive development.
Step-by-step explanation:
In the presence of the SRY gene, germ line cells in embryos with the Y chromosome become testes. The SRY gene, which is located on the short arm of the Y chromosome, is critical for initiating a series of events that directs the bipotential gonadal tissue to develop into testes. The testes then produce hormones such as testosterone, which further influence the development of the male reproductive system. In the absence of the SRY gene, which is typically the case in XX embryos, the gonads develop into ovaries instead. Thus, the SRY gene's function is crucial for sexual differentiation during embryonic development.