Meiosis, Germ Cells, and Fertilization
Meiosis, Germ Cells, and Fertilization
Meiosis, Germ Cells, and Fertilization
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The Sry Gene Directs the Developing<br />
Mammalian Gonad to Become a Testis<br />
• In egg-laying reptiles, the temperature of the incubating egg determines the<br />
sex of the offspring<br />
• The presence or absence of the Y chromosome determines the sex of the<br />
individual.<br />
• The Y chromosome directs the somatic cells of the genital ridge to develop<br />
into a testis.<br />
• the secreted signal protein Wnt4, for example, is required for normal<br />
mammalian ovary development.<br />
• The crucial gene on the Y chromosome is called Sry (sex-determining<br />
region of Y).<br />
• Sex-reversed mice cannot produce sperm, because they lack genes for<br />
sperm development.<br />
• Sry gene is introduced into the genome of an XX mouse zygote, the<br />
transgenic embryo produced develops as a male.<br />
• Sertoli cells are the main type of supporting cells in the testis.
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