Biopsychology

1. a) Describe the prenatal development of the sex organs (what happens for males? For females?), including what triggers the differentiation to begin. b) Choose one example of a syndrome where development of the sex organs does not progress in the typical fashion, and describe why the discrepancy between genotype and phenotype occurs. c) For individuals with that syndrome, is there reason to believe that their brains (and as a consequence, their behavior) may have undergone atypical sexual differentiation? (worth 25 points) pg. 328

a) The prenatal development of the sex organs of males and females begins with genes. Males have XY chromosomes while females have XX chromosomes. Throughout an early stage of prenatal development, both the male and the female have a group of Müllerian ducts as well as a group of Wolffian ducts, and gonads that are not distinguishable yet. Wolffian ducts are what come before other male reproductive organs which then become the vas deferens and seminal vesicles. Müllerian ducts are what come before the female internal structure that then develops into the oviducts, uterus, and upper vagina. The SRY gene is included in the male Y chromosome, which triggers the developing gonads to grow into testes, and these are the organs that make the sperm. The testes are developing and make androgens that will increase the growth of testes. Testes also make Müllerian inhibiting hormone (MIH) by around 12 weeks. This causes the penis and scrotum to develop as a result of the deterioration of the Müllerian ducts. Females on the other hand, do not have the SRY gene so the Wolffian ducts break down and then their gonads become ovaries, the organs that produce the egg. The testes of males produce more hormones of androgens, which are greater in amounts in males than estrogens which are hormones more abundant in females.

b) One example of a syndrome where the development of the sex organs does not progress in the typical fashion is congenital adrenal hyperplasia (CAH), which is when the adrenal gland from birth becomes overdeveloped. This is the most common cause of the intersex condition. This condition is caused by a genetic defect in which cortisol production leads to overstimulation of the adrenal gland. A hormone from the adrenal gland, cortisol, feeds back to reduce the release of adrenocorticotropic hormone (ACTH). More ACTH is being produced since the pituitary gland does not succeed in getting much cortisol as a feedback indicator.