Sex differentiation What makes us Male or Female?
Chromosomic Sex • Y Chromossome – SRY Gene – codes for the testis determining factor. In the absence of SRY there iare no testes. • X Chromossome – DSS – Double dose gene. Two DSS genes are required for the ovaries to be fully functional
Chromosomic number Full trisomy of an individual occurs when a chromosome fails to saparate during gamete formation. This can result in an extra or missing chromosome in a sperm or egg cell. After fertilization, the resulting fetus has 47/45 chromosome instead of the typical 46. Partial/mosaic • A partial trisomy occurs when part of an extra chromosome is attached to one of the other chromosomes, or if one of the chromosomes has two copies of part of its chromosome. • A mosaic trisomy is a condition where extra chromosomal material exists in only some of the organism's cells.
Sex chromosomes are special • You cannot have any monosomy of any chromosome other than X and Y. (in those cases you can function just fine) • Trisomies of sex chromosomes will be expressed mostly in the reproductive area; but not necessarily.
Bipotential Gonads • In the presence of SRY – Testes • In the absence of SRY – Ovary like • Two doses of DSS needed to develop fully functioning ovaries.
Brain • Presence of androgens – Brain – Male • Absence of androgens - Brain – Female
Brain Differentiation • In the presence of SRY – Testes • In the absence of SRY – Ovary like • Two doses of DSS needed to develop fully functioning ovaries.
Brain Lateralization corpus callosum
Size of the Anterior Commissure in the Brain It is a fiber tract that is larger in its midsagittal area in women than in man
What Makes Us Male or Female? • Chromosomic Sex • Gonadal Sex • Genital Sex • Brain Differentiation
Chromosomic defects XO – Turner XXY - Klinefelter
Turner Missing X Chromosome Low hair line
Klinefelter syndrome Extra X/Y Chromosome
Androgenized Genetic Female Child Genetic Female:XX External Genitalia exposed to Androgens during genital differentiation
Androgenized Genetic Female Child • Progestin Induced Virilization – androgens given to mothers to prevent miscarriages. • Congenital Adrenal Hyperplasia – need medical attention at birth. • Some anticonvulsant drugs • Pollutants?
Gender role preference behaviors in congenital adrenal hyperplasia patients
5-alpha reductase deficiency • 5 alpha reductase deficiency is one of several conditions where girls are bornwith XY genes (the usual male pattern). It is not known how common 5 alphareductase deficiency is, but it can run in families or it can be a chance event. • 5 alpha reductase deficiency is one of several conditions where girls are born with XY genes (the usual male pattern). It is not known how common 5 alpha reductase deficiency is, but it can run in families or it can be a chance event. • External genitalia female – testes present. Secondary Sex differentiation can include the growth of the clitoris (virilisation) and descending of the tests hirsutism. • In some parts of the world some girls born with this condition have changed to start living as a boy and man after puberty, but this is uncommon in Western Cultures.
Intersex • True hermaphrodites: have both gonads • Pseudo hermaphrodites: external genitalia does not mach internal gonodal sex.
Gender Identity • How a person perceives him/herself as male or female • Feeling of Maleness/femaleness or an ambivalence between the two.
Gender Identity disorder • Your concept of oneself (Male / Female) does not mach genitalia • Brain differentiation form of gender intersex?
"When you work with these kids, you see that they're not making a decision," he says. "They have always known. The sense of who one is--[boy or girl]--is a crucial existential aspect of humanity. It is powerful and inborn." The absence or presence of a penis is incidental. "The most important sex organ is the brain."Hopkins's William Reiner
Gender Dysphoria/Transsexualism • Gender differentiation of the Brain occurs on the 3rd Trimester of pregnancy. • Characterized by strong disgust for the body and deep uncertainty over the sense of self. • Gender identity (the sense of either being male or female) is not directly determined by the genetic code. • congenital intersex condition, in which the genitalia are spared prenatally but the brain is not. • Transsexual persons ordinarily do not have a mental illness. • A 1996 German study following 1422 gender-reassigned transsexual GID patients over a ten-year period found that less than 0.1% (1 in 1422) evidenced regret. • Standards of Care now calls triadic treatment (surgery, hormones and cross-living) medically indicated, medically necessary, and proven effective, in profound GID or transsexuality.
In the 60’s • Any XX infant, no matter how virilized, should be raised as a girl to preserve the chance of future fertility. A large, protruding clitoris should be reduced in size with a nerve-sparing recession or reduction rather than simple amputation. • Any undervirilized XY infant should be raised as a boy if the penis could be expected to be large enough to stand to urinate and to insert into a vagina for coitus. If it was too small or too malformed (e.g., cloacal exstrophy) for these functions, it was recommended that the baby be assigned as female, any gonads removed, a vaginal opening surgically constructed, and estrogen provided at puberty. • An infant with mixed chromosomes (e.g., mixed gonadal dysgenesis or true hermaphroditism) could be raised either way depending on appearance of genitalia and size of phallus. • Gender identity is set by 2 years of age and reassignment after that age should not be attempted unless requested by the patient.
Mid 90’s • Dozens of grown intersex patients complained publicly about unsatisfactory sexual function or incongruent gender identity, and criticized infant surgery for intersex conditions. Some have suggested that assignments be made more tentatively and surgery deferred in acknowledgement of the possibility of a desire to change gender when the child is older (see Re-assignment, below) • In 1997, the "rest of" David Reimer’s story was made public. He was the boy who had lost his penis to a surgical accident at 8 months in 1966, was reassigned from boy to girl at 18 months with further surgery to remove testes and estrogen treatment beginning at age 12. Although John Money had described the reassignment as a success in the 1970s, Reimer went public with his account of continuing to have a male gender identity despite the reassignment to a female sex of rearing. At age 15, Reimer reverted to living as a male. At age 38, he committed suicide. • There has been a significant swing in educated opinion back toward the importance of biological factors ("nature") in many aspects of human sexuality. • A large proportion of XY infants born with Cloacal extrophy and raised as female from early infancy have requested reassignment to male gender in late childhood and adolescence.
Today’s recomendations • Raise nearly all XX infants with functional ovaries as female. • The only rare exception would be completely and unambiguously virilized XX infants with Congenital Adrenal hyperplasia, who might be raised as male with genital surgery deferred. • Raise most ambiguous XY infants with testes as male unless the external genitalia are more female than male, marked androgen insensitivity is present, and testes are absent or defective. • Raise as male any biological male with unambiguous micropenis. • Raise as male any XY infant with functional testes and normal androgen sensitivity but malformed or absent penis. • Raise infants with mixed gonadal tissue, true hermaphroditism, or other chromosomal abnormalities as the sex most consistent with external genitalia, since gonads are usually nonfunctional. • Gender identity is set by 1-2 years of age and reassignment after that age should not be attempted unless requested by the patient.
Gender reassignment • http://www.youtube.com/watch?v=QeSvkE9ZtHk • Surgery
Biological indicators homosexuality Homosexuality has multiple causes • Genetic • Hormonal • Immunological
Dean Hamer and the Xq28 Genetic Markers • Hamer studied 40 pairs of homosexual brothers, and reported that 33 pairs shared a set of five X-linked genetic markers.
Fingerprints Gays and lesbians are also more likely to be left handed Both fingerprint patterns and Left-handedness are genetically determined
Gender differentiation period From: MacLusky and Naftolin, 1981 Animal Gestation or Incubation Critical Period Rat 20 – 22 18 – 27 days Mouse 19 – 20 Postnatal Guinea Pig 63 – 70 30 – 37 days Sheep 145 30 – 90 days Rhesus monkey 146 – 180 40 – 60 days Zebra finch 12 - 14 posthatching
Older brother effect • each older brother increases a man's odds of developing a homosexual sexual orientation by 28%–48%