Sex differences I

Question 1

What are organisational effects of sex hormones?

Answer 1

Permanent alterations in the body induced by a hormone at a critical period in development, occurring before birth.

Question 2

What are activational effects of sex hormones?

Answer 2

Hormone effects that occur in the fully developed organism after birth which depend on previous organisation effects.

Question 3

What is the first step in the process of the development of male sex organs?

Answer 3

1. A transcription factor called testis-determining factor is coded for by the SRY region on the Y chromosome. This protein binds to DNA in cells of undifferentiated gonads and causes them to become testes.

Question 4

What is the second step in the process of the development of male sex organs?

Answer 4

2. Testes produce the anti-Mullerian hormone that has defeminising effects and androgens that have masculinising effects.

Question 5

What is the Mullerian system?

Answer 5

A precursor of female internal sex organs

Question 6

What is the Anti-Mullerian hormone and what does it do in the masculinization process?

Answer 6

It is a peptide secreted by the foetal testes that act on that inhibits the development of the Mullerian system.

Question 7

Which two androgens are the primary causes of masculinization during early development?

Answer 7

testosterone and dihydrotestosterone

Question 8

Which androgens are responsible for development of the internal male sex organs?

Answer 8

testosterone

Question 9

Which androgens are responsible for the development of the external male genitals?

Answer 9

dihydrotestosterone

Question 10

Testosterone acts on androgen receptors in the cells of which system?

Answer 10

Wolffian system- the precursor of the male internal sex organs

Question 11

In the absence of the testes-determining factor, what happens?

Answer 11

Gonads develop into ovaries

Question 12

By default, primordial sex organs develop into..?

Answer 12

female sex organs

Question 13

The genetic sex of a human foetus is determined by…

Answer 13

The father’s sperm

Question 14

The prenatal development of female internal sex organs requires…

Answer 14

no hormones at all

Question 15

In XY sex reversal, point mutations in the SRY region on the Y chromosome, results in what?

Answer 15

Female sex organs in XY individuals

Question 16

Androgen insensitivity syndrome is a congenital condition in individuals with XY chromosomes. What phenotype does this produce?

Answer 16

A lack of androgen receptors causes development of a female however, the active anti-Mullerian system means that no internal sex organs are produced.

Question 17

Females with Turner’s syndrome have only one X chromosome and this results in…

Answer 17

lack of ovaries

Question 18

Lack of anti-Mullerian hormone in XY individuals causes the development of both male and female internal sex organs. What is the name of this syndrome?

Answer 18

Persistent Mullerian duct syndrome/ intersex

Question 19

Gonadotropic-releasing hormone(GnRH) is secreted by which structure in the brain?

Answer 19

hypothalamus

Question 20

GnRH acts on which gland in both males and females?

Answer 20

pituitary gland

Question 21

In males, GnRH causes the pituitary gland to secrete gonadotropic hormones (FSH and LH) which then causes what to happen?

Answer 21

the testis produce testosterone and male puberty occurs

Question 22

In females, GnRH causes the pituitary gland to secrete gonadotropic hormones (FSH and LH) which then causes what to happen?

Answer 22

the ovaries produce estradiol and female puberty occurs.

Question 23

What is sexual dimorphism?

Answer 23

It is a condition where the two sexes of a species exhibit differentiating characteristics beyond the different sex organs.

Question 24

William Young’s Organisational hypothesis aims to explain sex differences in brain and behaviour. What did he propose?

Answer 24

He proposed that early androgens, as well as affecting sex organs, also organise and develop the CNS in a masculine way causing masculinisation.

Question 25

What findings did William Young base his Organisational hypothesis on?

Answer 25

Experiments on female rats and guinea pigs, found that exposing them to androgens in utero during critical periods altered their adult sexual behaviour.

Question 26

Neural sexual dimorphisms have been demonstrated to depend on what?

Answer 26

Organisational effects of androgens alone, Activating effects of androgens alone and both. Environmental influences also may play a role

Question 27

Many masculinising effects of testosterone were found to be mediated by oestrogen in which type of animals?

Answer 27

rodents

Question 28

Following on from the findings that oestrogen also has a masculinising effect on the brain and behaviour in rodents, what hypothesis was proposed?

Answer 28

Aromatisation hypothesis

Question 29

What does the Aromatisation hypothesis propose happens during masculinisation?

Answer 29

testosterone is converted to oestrogen by an enzyme called aromatase before it acts on oestrogen receptors in the nuclei of some CNS cells.

Question 30

In response to the Aromatisation hypothesis, which hypothesis was introduced to account for the feminising effects of oestrogen?

Answer 30

Protection hypothesis

Question 31

What does the Protection hypothesis state?

Answer 31

The brains of developing rodents are protected from the masculinising effects of oestrogen by an oestrogen-binding protein called alpha-fetoprotein in the blood. This protein prevents testosterone from binding to oestrogen receptor and exerting it's masculinsing effects.