Lecture 4

Question 1

What are the 5 levels of sex determination?

Answer 1

• chromosomal sex
• gonadal sex
• hormonal sex
• morphological sex
• behavioural sex

Question 2

Sex differences are (increased/reduced) in monogamous species

Answer 2

REDUCED

Question 3

Chromosomal sex is defined during ____

Answer 3

fertilization

Question 4

Each embryo develops a thickening called the _____ on the ventromedial surface of each ____

Answer 4

germinal ridge; protokidney

Question 5

Why do we call the germinal ridge a bipotential primordial organ?

Answer 5

• has potential to become ovary or testis

Question 6

Expression of the ___ gene found on the Y chromosome produces testis determination factor (TDF)

Answer 6

SRY

Question 7

The protein products of SRY and _____ lead to the development of the (inner/outer) part of the germinal ridge and (testes/ovaries) are formed

Answer 7

SOX9; inner; testes

Question 8

If SRY and ___ are not present, the (inner/outer) part of the germinal ridge develops and (testes/ovaries) are formed

Answer 8

SOX9; outer; ovaries

Question 9

Some recent evidence suggests that ____ can directly influence sexually dimorphic brain anatomy/function (not mediated by hormonal environment!)

Answer 9

chromosomal sex

Question 9

Why do we call female the default sex?

Answer 9

• in absence of gonads, development follows a female pathway
• need androgens from gonads to initiate male dev.

Question 10

The ____ and ___ duct systems are normally both present early in embryonic development. We call this a _____

Answer 10

Mullerian and Wolffian; dual anlagen

Question 11

If there is no ____ or ____, the ____ duct system develops into the fallopian tubes, uterus, and upper vagina.

Answer 11

MIH (mullerian inhibiting hormone) or androgen
Mullerian duct system

Question 12

___ stimulates the development of the ___ duct system (__) and ___ causes the regression of the Mullerian duct system (____)

Answer 12

testosterone, Wolffian (masculinization)
MIH (defeminization

Question 13

You can see the sex of an embryo on an ultrasound at approx __ months

Answer 13

4

Question 14

____ are responsible for the differentiation of external genetalia

Answer 14

androgens

Question 15

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 ____

Answer 15

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

Question 16

Mating behaviour for both sexes is under the control of ____

Answer 16

gonadal steroid hormones

Question 17

(T/F) if you inject adult female mice w testosterone, their mounting behaviour increases to male-typical levels

Answer 17

FALSE (demasculinization occurs at some point in dev where they lose potential to display male sexual behaviour)

Question 18

What is the first version of the organizational/activational hypothesis of sexually dimorphic behaviours?

Answer 18

• 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

Question 19

What were the findings of William Young that led to the development of the organizational/activational hypothesis of sexually dimorphic behaviours?

Answer 19

• 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

Question 20

There is pulsatile release of LH in (males/females)

Answer 20

both! (but females also have cyclical release that peaks at ovulation)

Question 21

Gonadal function is driven by ___ secreted from the anterior pituitary. The system functions as a (pos/neg) feedback loop.

Answer 21

gonadotropins; negative

Question 22

How is the negative feedback loop of sex hormones altered in females?

Answer 22

• escape neg loop on cyclical basis
• after ovulation, neg feedback mechanisms are engaged

Question 23

Partial expression of the SRY gene leads to ___

Answer 23

incomplete gonadal differentiation (ovotestis)

Question 24

Swyer syndrome is characterized by ______ in XY individuals that lack the ___ gene. External genitalia ressembles ____ and gonads ____.

Answer 24

failure of sex glands (gonads) to develop in XY indivs lacking SRY gene
external genitalia ressembles female; gonads don’t function

Question 25

What are the key differences between how the concealment-centered model and the patient-centered model look at intersex?

Answer 25

• 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

Question 26

genetic males born w 5a(alpha)-reductase deficiency are born with ____ genitalia and are usually labeled and reared as _____. What happens during puberty?

Answer 26

• ambiguous genitalia and small undescended testes
• labeled girls at birth
• at puberty, T masculinizes body and genitalia start to resemble male-typical penis/scrotum

Question 27

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

Answer 27

lack X chromosome X0 or damage to second X (or Y)
female

Question 28

In congenital adrenal hyperplasia, a lack of 21-Hydroxylase enzyme leads to _____. This causes _____ in genitals.

Answer 28

overproduction of adrenal androgens
moderate-severe masculinization in genitals of affected females

Question 29

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 _____

Answer 29

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)

Question 30

What were the 3 examples of trisomic anomalies discussed?

Answer 30

• 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

Question 31

WHat does the more modern version of the organizational/activational hypothesis of hormonal sex differentiation add?

Answer 31

• organizational window extended to pre-pubertal period
• much less fixed, includes other factors like environment and direct effect of chromosomes