PSYB64H3 Study Guide - Sexually Dimorphic Nucleus, Sexual Dimorphism, Chromosome Abnormality

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Overview: sexual development, hormones & sexual behaviour, sex differences in nervous system, sexual orientation, attraction, sexual dysfunctions. Twenty-three pairs of chromosomes are found in the nuclei of all human body cells except red blood cells (which have no dna) and sperm and egg cells (which contain only one copy from each pair of chromosomes). Differentiation of gonads and external genitals (figure 10. 4) During the first six weeks after conception, the primordial gonads are undifferentiated. Subsequently, testis-determining factor encoded by the sry gene on the y chromosome will begin to turn the undifferentiated gonads into testes in males. The testes begin to release androgens, causing the external genitalia to develop into a penis and scrotum. Alternate genes guide the development of female gonads into ovaries. In the absence of androgens, the female external genitalia develop into clitoris, labia, and vagina. Sexual chromosome abnormalities: turner syndrome (xo) 2 in 2500 live births: klinefelter syndrome (xxy) 1. 79 out of 1000 male births: xyy.