Sexual Differentiation Flashcards Preview

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Flashcards in Sexual Differentiation Deck (33):
1

What is genetic sex?

Chromosomal constitution

XX = female
XY = male

2

Why do we need sex?

Allows genetic material to undergo recombination and allelic assortment to generate variation in populations that allows adaptation to changing selective pressure

3

What is gonadal sex?

Ovary or testis

Determined by genetic sex of indifferent gonad

4

What is somatic sex?

External genitalia and phenotype

Determined by gonadal sex through messengers (eg. hormones)

5

What is the chromosomal constitution of Turner's syndrome?

XO

6

What is the chromosomal constitution of superfemale?

XXX

7

What is the chromosomal constitution of Kleinfelter's syndrome?

XXY

8

What is the chromosomal constitution of supermale?

XYY

9

What is the key factor in establishing the effect of the Y chromosome?

SRY

Sex-determining region of the Y chromosome

10

How big is the SRY protein?

223 amino acids

Conserved DNA binding domain of 79 amino acids (HMG box)

Binds to both DNA and RNA, affecting their accessibility and stability

11

What are the effects of SRY?

Affects expression of a number of other genes, eg. SOX9

Causes differentiation of Sertoli cells and Leydig cells

12

When do the genital ridges form?

During 5th and 6th weeks of development

13

How do the genital ridges form?

Colonised by primordial germ cells migrating from extraembryonic mesoderm close to yolk sac

14

What do Sertoli cells do?

Make Mullerian Inhibitory Substance (MIS)

15

What does MIS do?

Destabilises paramesonephric ducts

16

What do Leydig cells make?

Testosterone

17

What does testosterone do?

Stimulates formation of mesonephric ducts

18

What happens in the absence of MIS?

Female genital ridge develops down default pathway and forms ovary

Mesonephric ducts degenerate

Paramesonephric ducts form oviduct, uterus and upper part of vagina

19

What do the mesonephric ducts form?

Vas deferens

20

What is primary hermaphroditism?

Anomalies of the gonad

Ovary on one side and testis on the other

Mixed ovarian testicular tissue in one or both gonads due to chromosome mosaicism

21

What is secondary hermaphroditism?

Anomalies of the soma

1. CAIS
2. Congenital adrenal hyperplasia
3. Micropenis
4. Hypospadias

22

What is complete androgen insensitivity syndrome (CAIS)?

XY

Testes but female soma

Receptors insensitive to testosterone so lack of male sexual characteristics

No uterus, fallopian tubes or upper vagina due to normal MIS

23

What is micropenis?

Poorly developed phallus

24

What is hypospadias?

Urethra opens in ventral penis or in vagina

25

What is congenital adrenal hyperplasia?

Impaired cortisol secretion leads to increased ACTH levels due to loss of negative feedback

Results in hyperplasia of adrenal cortex

26

What causes congenital adrenal hyperplasia?

Deficiency of 21-hydroxylase, which breaks down 17-hydroxyprogesterone to 11-deoxycortisol

Cortisol precursors accumulate in excess and are converted to androgens

27

What are the effects of congenital adrenal hyperplasia?

In utero virilisation of female fetus genitalia

28

What is gender identity?

An internal state of being - psychological quality

How people think of themselves and identify in terms of sex

29

What is gender role?

Everything we do that communicates our sex/gender to others

Social gender

30

At what age does gender identity develop?

By 2 years

31

What is sexuality?

The part of our emotional and intellectual make up concerned with the erotic

32

What is paraphilia?

Finding non-human stimuli or behaviours sexually arousing

33

How does androgen exposure affect sexuality in females?

Greater prevalence of homosexuality in CAH girls