Sex Determination and Differentiation Flashcards
biological sex, the physical body
sex
- essentially the “biological and physiological characteristics that distinguish females from males”
self identification of being intrinsically male, female or alternative gender
gender
- this includes “socially constructed roles, relationships, behaviors, relative power and other traits societies ascribe to women and men”
is the early developmental event that dictates whether a fetus will be male or female
- chromosome driven
sexual determination
early process in which a fetus begins to develop a male or female body and behaviors
- hormone driven
sexual differentiation
if the sperm that enters the egg has a Y chromosome, the offspring will become male
- SRY gene (sex determining region on the Y chromosome) is responsible for the development of testes)
how is sex determined?
if the sperm carries an X chromosome, the offspring will become female, without the SRY gene:
ovaries form
the … develop into the internal male reproductive structures (epidiymis, vas deferens and seminal vesicles) and the Mullein ducts regress, which is driven by testosterone from the testes
Wolffian ducts
the … (which develops into the female reproductive structures of Fallopian tubes, uterus and vagina) shrinks because of the anti-mullerian hormone (AMH) from the testes
Mullerian ducts
testosterone can be converted to 2 other hormones: … (an enzyme) converts T into dihydrotestosterone (DHT); required for external male genitalia masculinization
- … converts T in estradiol (E) responsible for masculinizing the brain
5a-reductase and aromatase
in … a person only has one sex chromosome – a single X
- a feminine body develops due to lack of the SRY gene, with abnormal ovaries (no steroid hormone production or eggs)
- estrogen treatment at puberty induces breast growth and a female-typical puberty
Turners Syndrome
androgen insensitivity syndrome (AIS) occurs in XY individuals with defective androgen receptors (so, androgens cannot have action)
- testes because of the SRY gene on the Y chromosome
- T (and also DHT), AMH
- Female
will they develop testes or ovaries?
what hormones will be produced? which will act?
what will be the phenotype of the individual?
pronounced differences in appearance between male and females
- reproductive structures
- differences in the brain
- size, connectivity, number of neurons, neural density, etc
- These differences are due to early exposure to hormones
sexual dimorphism
- occurs before the brain matures
- critical/sensitive period
- permanent effects
- structural changes in the brain
organizational effects of hormones
in adulthood is affect by organizational hormones AND the circulating hormones in aduthood that act upon (or activate) the circuitry that was organized during the critical period
behavior
- occurs in adulthood
- no sensitive period
- transitory (short-acting)
- biochemical changes
activational effects of hormones
yes!!
the deciding factor for what kind of effect the hormone will have is:
can the same hormone be both organizational AND activational?
the timing of its action (steroid hormones have an organizational effect only when present during the critical period of development)
depending on the species and the behavior, this period may be before birth or just afterwards, in the … period
neonatal
two possible influences on gender identity and sexual orientation
- socialization
- biology
the more older brothers a boy has, the more likely he is to grow up to be gay
- this is only true for biological brothers sharing the same mother
- the effect looks like it may be driven by the mother’s immune system with subsequent pregnancies
fraternal birth order effect
IMPORTANTLY: a persons identity and orientation are influenced by a variety of factors:
biology is only one of those factors
