3.2 The Role Of Chromosomes And Hormones In Sex And Gender

Question 1

How many pairs of chromosomes do humans have?

Answer 1

23 pairs

Question 2

What determines sex?

Answer 2

sex chromosomes

Question 3

What sex chromosomes does a female have?

Answer 3

XX

Question 4

What sex chromosomes does a male have?

Answer 4

XY

Question 5

What causes male physical development at the fetal stage?

Answer 5

presences of the SRY gene on the Y sex chromosome

Question 6

What does SRY stand for?

Answer 6

Sex-determining region Y protein

Question 7

How does the SRY function?

Answer 7

The SRY gene creates a transcription factor that binds to DNA to control other genes (this is an epigenetic change)

Question 8

Explain the process of male sex development.

Answer 8

Every fetus appears the same until a few weeks after the conception event
Sex organ development is complete at around 3 months after conception
Lutropin is then produced in both sexes in the adrenal glands
Testes contain Leydig cells, which respond to lutropin by producing testosterone
Testosterone drives further male development

Question 9

What broad term can be used to determine atypical sex chromosome patterns?

Answer 9

intersex

Question 10

In how many males can Klinefelter’s syndrome be found?

Answer 10

1 in 10,000 males

Question 11

What is Klinefelter’s syndrome?

Answer 11

This is an XXY configuration
Child born with penis and develops male traits
There are usually infertile, lack muscular definition and have feminized masculine characteristics (e.g. slim jaw, less facial hair, sometimes even breast tissue.)

Question 12

In how many females can Turner’s syndrome be found?

Answer 12

1 in 2,000 females

Question 13

What is Turner’s syndrome?

Answer 13

This is due to ‘XO’ rather than XX or XY - one sex chromosome is damaged or missing
Born with both vagina and womb but underdeveloped ovaries
No monthly period, physically short/stout build
Can have webbed neck, narrow hips, irregular internal organs, nevi (chronic skin lesions)

Question 14

When does testosterone production begin?

Answer 14

Production of testosterone begins before birth

Question 15

What happens if a fetus is insensitive to testosterone?

Answer 15

Born as intersex
No formation of male genitalia
Often born/raised as girls because no penis/testicles are visible
Some are identified as XY and raised as boys

Question 16

What effect does a surge of testosterone have on males in puberty?

Answer 16

Drives the production of secondary male characteristics

Question 17

How can a fetus’ brain development be affected if their mother has elevated levels of testosterone?

Answer 17

Studies show XX females are ‘tomboyish’ and prefer masculine activities in this case (Berenbaum & Bailey, 2003)
XY males have more pronounced male characteristics

Question 18

What effect does estrogen levels have on brain size?

Answer 18

Associated with smaller brain size (Shi et al. 2015)

Question 19

When is oestrogen present in the fetus?

Answer 19

Present in all cases as female is the default gender

Question 20

What female hormone promotes secondary female characteristics in puberty?

Answer 20

Oestrogen

Question 21

When are levels of oestrogen particularly elevated?

Answer 21

During pregnancy

Question 22

What effect does oestrogen have on menstruation?

Answer 22

Controls blood flow through increasing blood flow to uterus

Question 23

When and where is oxytocin produced?

Answer 23

Produced in the pituitary gland in response to skin-to-skin contact (e.g. breastfeeding)

Question 24

What effect can oxytocin have?

Answer 24

Promotes bonding behaviours
Causes milk production
Enables post-orgasm bliss/contentment
Helps in wound-healing
Oxytocin dampens flight-or-fight response in women (not in men, due to testosterone) and is related to 'tend and befriend' (Taylor et al, 2000)

Question 25

what are chromosomes

Answer 25

the X-shaped bodies that carry all the genetic information (DNA) for an orgaism

Question 26

what are hormones, can you give some examples of the processes they influence?

Answer 26

the body’s chemical messengers.
they travel through the bloodstream, influencing many different processes, including mood, the stress response and bonding between mother and babt

Question 27

define intersex?

Answer 27

the term used to describe an individual who is neither distinctly male nor female because of a mismatch between, for example, chromosomes and genitals

Question 28

summarise the role of sex chromosomes in sex and gender

Answer 28

usually genetic sex determines genitalia - all foetuses start off with female genitalia
genes determine genitalia and also which hormones, in turn leads to the gender behaviours
atypical sex chromosomes - Klinefelter’s syndrome (XXY), low levels of testosterone mean less body hair and infertility, taller than average, less muscular co-ordination
Turner’s syndrome (XO) - underdeveloped ovaries, short stature, no monthly period, may have other unusual physical characteristics, e.g. small lower jaw

Question 29

summarise the role of hormones in sex and gender

Answer 29

hormones govern gender development
testosterone effects - XY’s insensitive to testosterone and then born with no penis (classed as females) and in XX’s exposed prenatally to testosterone who show masculine behaviour (Berenbaum and Bailey)
oestrogen - not required to direct prenatal genital development, may lead to smaller brain size. oestrogen is important for female secondary sexual characteristics e.g. breast development

Question 30

evaluate the role of chromosomes and hormones in sex and gender

Answer 30

challenging biological determinism - Money’s sex-of-rearing view important but evidence show genetic sex is most significant
importance of other factors - no simple formula, e.g CAH individuals are XX but exposed to male hormones, many content with their gender assigned at birth
role of culture - Batistas, boys sex-typed as girls but adjusted to male role when male genitalia appeared because culture had more fluid notion of gender
real world applications - avoid early surgery (intersex society), give hormone supplements, e.g for Turner’s syndrome, Olympic Games committee uses physical characteristics (Brown)
effects of hormones on brain development: female monkeys showed more rough-and-tumble play when exposed to testosterone.
however Eisenegger et al. showed that expectations might explain human behaviour better