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Human Reproduction > Sexual Differentiation > Flashcards

Sexual Differentiation Flashcards

1
Q

What is genetic sex?

A

Chromosomal constitution

XX = female
XY = male
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2
Q

Why do we need sex?

A

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

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3
Q

What is gonadal sex?

A

Ovary or testis

Determined by genetic sex of indifferent gonad

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4
Q

What is somatic sex?

A

External genitalia and phenotype

Determined by gonadal sex through messengers (eg. hormones)

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5
Q

What is the chromosomal constitution of Turner’s syndrome?

A

XO

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6
Q

What is the chromosomal constitution of superfemale?

A

XXX

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7
Q

What is the chromosomal constitution of Kleinfelter’s syndrome?

A

XXY

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8
Q

What is the chromosomal constitution of supermale?

A

XYY

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9
Q

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

A

SRY

Sex-determining region of the Y chromosome

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10
Q

How big is the SRY protein?

A

223 amino acids

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

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

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11
Q

What are the effects of SRY?

A

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

Causes differentiation of Sertoli cells and Leydig cells

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12
Q

When do the genital ridges form?

A

During 5th and 6th weeks of development

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13
Q

How do the genital ridges form?

A

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

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14
Q

What do Sertoli cells do?

A

Make Mullerian Inhibitory Substance (MIS)

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15
Q

What does MIS do?

A

Destabilises paramesonephric ducts

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16
Q

What do Leydig cells make?

A

Testosterone

17
Q

What does testosterone do?

A

Stimulates formation of mesonephric ducts

18
Q

What happens in the absence of MIS?

A

Female genital ridge develops down default pathway and forms ovary

Mesonephric ducts degenerate

Paramesonephric ducts form oviduct, uterus and upper part of vagina

19
Q

What do the mesonephric ducts form?

A

Vas deferens

20
Q

What is primary hermaphroditism?

A

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
Q

What is secondary hermaphroditism?

A

Anomalies of the soma

  1. CAIS
  2. Congenital adrenal hyperplasia
  3. Micropenis
  4. Hypospadias
22
Q

What is complete androgen insensitivity syndrome (CAIS)?

A

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
Q

What is micropenis?

A

Poorly developed phallus

24
Q

What is hypospadias?

A

Urethra opens in ventral penis or in vagina

25
Q

What is congenital adrenal hyperplasia?

A

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

Results in hyperplasia of adrenal cortex

26
Q

What causes congenital adrenal hyperplasia?

A

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

Cortisol precursors accumulate in excess and are converted to androgens

27
Q

What are the effects of congenital adrenal hyperplasia?

A

In utero virilisation of female fetus genitalia

28
Q

What is gender identity?

A

An internal state of being - psychological quality

How people think of themselves and identify in terms of sex

29
Q

What is gender role?

A

Everything we do that communicates our sex/gender to others

Social gender

30
Q

At what age does gender identity develop?

A

By 2 years

31
Q

What is sexuality?

A

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

32
Q

What is paraphilia?

A

Finding non-human stimuli or behaviours sexually arousing

33
Q

How does androgen exposure affect sexuality in females?

A

Greater prevalence of homosexuality in CAH girls

Human Reproduction (17 decks)

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