Bio 27: September 26, 2012

1. Bio 27: September 26, 2012 Chapter 5: Gender Issues

2. Exam grades • Mean exam score: 61.2% (D) • Median exam score: 65% (C) • Grading scheme: ≥85% = A 75–84.99% = B 65–74.99% = C 50–64.99% = D <50% = F

3. Course grades • Mean course score: 69.32% (C) • Median course score: 75.93% (B) • Grading scheme: ≥85% = A 75–84.99% = B 65–74.99% = C 50–64.99% = D <50% = F

4. Sex and Gender: some definitions • Sex: biological female or maleness • genetic sex: determined by sex chromosomes • anatomical sex: determined by physical differences • Gender: psychosocialmeaning of maleness and femaleness; masculinity or femininity • Gender Identity: each person’s subjective sense of being male or female • Gender Roles: the cultural norms for male and female behavior

5. Chromosomal sex • Humans have 23 pairs of chromosomes • 22 autosomes and 1 sex chromosome • Chromosomal sex • XX: female • DSS gene on X • XY: male • SRY gene on Y • XXX: female • X only : female • Y only: lethal

6. Gonadal sex • We all begin life with gonads that are not sex-specific! • The SRY gene on the Y chromosome, if present, encodes proteins that initiate the conversion of the gonads into testes • In the absence of the SRY gene, the gonads become ovaries

7. Hormonal sex • Once they begin to differentiate the gonads start to secrete hormones: • Ovaries: mostly estrogens and progestins • Testes: mostly androgens, including testosterone • These hormones influence development of the internal & external genitalia

8. Hormones promote differentiation of the internal genitalia Androgens present: disappearance of the Müllerian duct and maturation of the Wolffian duct Androgens absent: disappearance of the Wolffianduct and maturation of the Müllerianduct

9. Hormones promote differentiation of the external genitalia

10. Homologous Sex Organs

11. Sex differences in the brain • Females and males have differences in their brain structure; these differences seem to be influenced by androgens (testosterone) and estrogens • These differences include: • Males have slightly larger brains than females • A region of the brain called the hypothalamus seems to become less sensitive to estrogens in males • An area of the hypothalamus called the bed nucleus of the striaterminalis (BST) is sensitive to androgens and estrogens and seems to influence sex differences and sexual functioning • Another area of the hypothalamus, the preoptic area (POA), also shows differences in men and women

12. Other brain areas also differ • Cerebral cortex is the brain area associated with “higher mental processes” like memory, perception, and thought • The left and right sides of the cortex show specialization; the two sides are connected by a structure called the corpus callosum • Males tend to have a larger right cortex and females a larger corpus callosum • Women and men tend to use their brains differently when solving problems

13. Male and female brains? • Findings of differences in brain function in males and females are controversial • Our brains learn things by physically changing; our brains respond to many stimuli, including social messages • Females often tend to score higher in verbal skills, and males in math skills, although females and males typically have similar math scores until around puberty • Are these innate differences or learned differences?

14. Typical Prenatal Differentiation

15. atypical prenatal differentiation

16. Intersexed individuals • Intersexed individuals are classified as: • True hermaphrodites: have both ovarian and testicular structures in their bodies; extremely rare! • Pseudohermaphrodites: occurs 1 in every 2,000 births; have gonads that match chromosomal sex but ambigulous internal and external genitalia

17. Atypical Prenatal Differentiation • Sex chromosome disorders: • Turner’s syndromeXO: 1 in every 2500–3000 females; develop typical female external genitals, but internal genitalia and gonads are not fully developed. Women with this syndrome do not develop breasts at puberty or menstruate. • Klinefelter’s syndromeXXY: 1 in every 1000 males; develop male external genitalia, but are typically sterile with smaller than normal penises and testes. Usually identify as male but some have gender-identity issues

18. Disorders affecting prenatal hormonal processes • Androgen insensitivity syndrome (AIS): Individuals are chromosomally male, but due to a mutation in their androgen receptors develop as females; have “blind” vaginas and undescended, undeveloped testes

19. Atypical Prenatal Differentiation

20. Homework assignment #3: due at the beginning of class 10/3/12 What people and other influences have influenced your own gender role development? Think about both positive and negative influences that shaped your gender role. What do you feel are the benefits and consequences of being the gender you are? 400-700 words