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PSYB64H3 (201)
Chapter 10


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Janelle Leboutillier

START FOR FINAL EXAM! PSYB64: Chapter 10 (Sexual Behaviors) lecture 7 Sexual development - X chromosome from mother to all their offspring; 2 X = female - Y chromosome from father (with an X); 1 X & 1 Y = male - Human genome 23 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) Sex Chromosome Abnormalities 1. Turner Syndrome single chromosome (XO) instead of XX or XY 1 in 2500 live births lack of 2 sex chromosome = impact on fertility. Growth, and hormone production and is associated with higher risk of diabetes, osteoporosis, and cardiovascular disease have normal female external genitalia but ovaries develop abnormally (from unidentified regions on X chromosomes and having a single X interferes) may be infertile may be relatively short specific deficits in spatial relationships and memory human growth hormone, female hormone replacement therapy, etc. 2. Klinefelter syndrome - 1.79 out 1000 male births - XXY Genotype - Male but reduced fertility and require hormone treatment at puberty to promote the development of secondary male sex characteristics (facial hair, deeper voice, development of external genitalia) and to inhibit female characteristics such as breast development due to interference with the process of x-inactivation in which one X chromosome in each female cells is randomly SILENCED. - Mild cognitive difficulties (delayed and reduced verbal skills) and social awkwardness - Left-handedness is common affect brain lateralization or localization of specific functions such as language in one hemisphere 3. XYY - 1 in 1000 male births - physical and behavioral correlates of condition are typically subtle 1 - physically within the limit but taller and leaner, acne and minor physical abnormalities of the eye, elbow, and chest - average IQ scores are slightly below the average of males - fertile but more likely typical to produce sperm with sex chromosome abnormalities - controversial antisocial behaviors (eg. Speck killed 18 student nurses! & 17 men property crimes rather than violent crimes.) Three stages of Prenatal Development 1. Development of Gonads th - until 6 week after conception - develop into either ovaries (female gonads) and testes (male gonads) - sex-determining region of Y chromosome (SRY) = gene on the short arm of T chromosome expressed in male embryos that encodes for testis-determining factor - testis-determining factor = protein encoded by SRY gene on Y chromosome that turns the primordial gonads to develop into testes - mice: lack SRY gene = develop ovaries and SRY gene = testes 2. Differentiation of Internal Organs - 3 month of development - wolffian system = males internal system that develops into seminal vesicles, vas deferens and prostate gland testosterone (a kind of androgen = steroid hormone that develops and maintains typically masculine characteristics) promotes the development of Wolffian system - Mullerian system = females internal system that develops into a uterus, fallopian tubes and upper two thirds of the vagina in the absence of anti- Mullerian hormone ovaries are not active during fetal development unlike testes - Androgen insensitivity syndrome (AIS) = disrupts normal Wolffian system in males = defective gene produces abnormal androgen receptors = tissues of fetus are blind to presence of androgen (have normal XY genotype and testes) = lack of functional androgen receptors prevents Wolffian system development = anti-mullerian hormone prevents Mullerian system development = shallow vagina and no ovaries, fallopian tubes or uterus (from Mullerian system, which is responsible for upper 2/3rds of vagina) = infertile = genetic males but have female appearance and strong female gender identities = many marry and engage in normal female behaviour 2= competing at international levels of sports 3. Development of External Genitalia o male: penis and scrotum o female: clitoris, labia and outer part of vagina o hormonal stimulation is essential for male external genitalia development (not in female) o 5-alpha-di-hydrotestosteroen androgen secreted by testes that masculinizes the external genitalia to develop normally produced from reaction between testosterone and 5-alpha- reductase o Congenital adrenal hyperplasia (CAH) recessive heritable condition in which the fetuss adrenal glands release elevated levels of androgens, resulting in masculinization of external genitalia and some cognitive behaviors in affected female [ Males with CAH few observable traits because fetus are already exposed to androgens ] Females with CAH born with ambiguous external genitalia (clitoris is enlarged, labia look similar to a scrotum and in some cases there is no vaginal opening) Tomboys, bisexual, etc. majority are heterosexual Development at Puberty - secondary sex characteristics o characteristics related to sex that appear at puberty, i
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