Lecture 4 Flashcards
What are the 5 levels of sex determination?
- chromosomal sex
- gonadal sex
- hormonal sex
- morphological sex
- behavioural sex
Sex differences are (increased/reduced) in monogamous species
REDUCED
Chromosomal sex is defined during ____
fertilization
Each embryo develops a thickening called the _____ on the ventromedial surface of each ____
germinal ridge; protokidney
Why do we call the germinal ridge a bipotential primordial organ?
- has potential to become ovary or testis
Expression of the ___ gene found on the Y chromosome produces testis determination factor (TDF)
SRY
The protein products of SRY and _____ lead to the development of the (inner/outer) part of the germinal ridge and (testes/ovaries) are formed
SOX9; inner; testes
If SRY and ___ are not present, the (inner/outer) part of the germinal ridge develops and (testes/ovaries) are formed
SOX9; outer; ovaries
Some recent evidence suggests that ____ can directly influence sexually dimorphic brain anatomy/function (not mediated by hormonal environment!)
chromosomal sex
Why do we call female the default sex?
- in absence of gonads, development follows a female pathway
- need androgens from gonads to initiate male dev.
The ____ and ___ duct systems are normally both present early in embryonic development. We call this a _____
Mullerian and Wolffian; dual anlagen
If there is no ____ or ____, the ____ duct system develops into the fallopian tubes, uterus, and upper vagina.
MIH (mullerian inhibiting hormone) or androgen
Mullerian duct system
___ stimulates the development of the ___ duct system (__) and ___ causes the regression of the Mullerian duct system (____)
testosterone, Wolffian (masculinization)
MIH (defeminization
You can see the sex of an embryo on an ultrasound at approx __ months
4
____ are responsible for the differentiation of external genetalia
androgens
In the presence of androgens, the ____ fuses, the ___ develops into a penis, and the ____ fuse into the scrotum
In the absence of androgens, a clitoris develops from the ____ and vaginal labia develop from the ____
urethral groove fuses, genital tubercle develops into a penis, and the genital folds fuse into the scrotum
clitoris develops from genital tubercle and vaginal labia develop from the genital folds
Mating behaviour for both sexes is under the control of ____
gonadal steroid hormones
(T/F) if you inject adult female mice w testosterone, their mounting behaviour increases to male-typical levels
FALSE (demasculinization occurs at some point in dev where they lose potential to display male sexual behaviour)
What is the first version of the organizational/activational hypothesis of sexually dimorphic behaviours?
- sex hormones act during prenatal stage to irreversibly organize the nervous system in a sex-specific manner
- during adult life, the same hormones have activation effects
What were the findings of William Young that led to the development of the organizational/activational hypothesis of sexually dimorphic behaviours?
- study where they injected T into pregnant guinea pigs
- those exposed to T prenatally were less likely to display lordosis in adulthood
- were more likely to display mounting behaviour in response to T therapy as adults
There is pulsatile release of LH in (males/females)
both! (but females also have cyclical release that peaks at ovulation)
Gonadal function is driven by ___ secreted from the anterior pituitary. The system functions as a (pos/neg) feedback loop.
gonadotropins; negative
How is the negative feedback loop of sex hormones altered in females?
- escape neg loop on cyclical basis
- after ovulation, neg feedback mechanisms are engaged
Partial expression of the SRY gene leads to ___
incomplete gonadal differentiation (ovotestis)
Swyer syndrome is characterized by ______ in XY individuals that lack the ___ gene. External genitalia ressembles ____ and gonads ____.
failure of sex glands (gonads) to develop in XY indivs lacking SRY gene
external genitalia ressembles female; gonads don’t function
What are the key differences between how the concealment-centered model and the patient-centered model look at intersex?
- concealment: it is a pathology that requires immediate medical attention; gender is only determined by nurture so can just make them “look” like girl or boy and raise them that way
- patient: not a medical problem, let kids grow up and make their own choices about medical treatments
genetic males born w 5a(alpha)-reductase deficiency are born with ____ genitalia and are usually labeled and reared as _____. What happens during puberty?
- ambiguous genitalia and small undescended testes
- labeled girls at birth
- at puberty, T masculinizes body and genitalia start to resemble male-typical penis/scrotum
Turner syndrome is a condition in which individuals lack _____. They have a (female/male) external experience but gonadal dev is limited and they usually don’t attain puberty w/o medical attention
lack X chromosome X0 or damage to second X (or Y)
female
In congenital adrenal hyperplasia, a lack of 21-Hydroxylase enzyme leads to _____. This causes _____ in genitals.
overproduction of adrenal androgens
moderate-severe masculinization in genitals of affected females
In androgen insensitivity syndrome, a mutation on the X chromosome causes ____ to be absent. (XX/XY) individuals w the condition have normal-appearing (male/female) genitalia and are sexed and reared as ___. The condition is usually discovered in _____
functional androgen receptors are absent
XY only are affected (XX have other unaffected X)
genitalia looks female; reared as girls
usually discovered in puberty bc no period (no uterus)
What were the 3 examples of trisomic anomalies discussed?
- Klinefelter syndrome (XXY): often sterile, learning disability
- XYY: considered male @ birth but often sterile, taller, risk of ID (more likely to be prosecuted)
- XXX: often mild-no symptoms, sometimes LD
WHat does the more modern version of the organizational/activational hypothesis of hormonal sex differentiation add?
- organizational window extended to pre-pubertal period
- much less fixed, includes other factors like environment and direct effect of chromosomes
