3.0 Sexual Differentiation Flashcards Preview

MedST IB: Human Reproduction (HR) > 3.0 Sexual Differentiation > Flashcards

Flashcards in 3.0 Sexual Differentiation Deck (23)
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Why did evolution favour sex?

Recombination and allelic assortment helps to generate variation in populations (allows adaptation)


What determines gonadal sex?

Genetic sex


What determines somatic sex?

Gonadal sex affects somatic sex

This is done through messengers
- Can be paracrine peptide molecules
- Or endocrine molecules


What is the autosomal number, sex chromosomes and gonads present for the following conditions:
1) Turner's syndrome
2) Female
3) Superfemale
4) Male
5) Klienfelter's syndrome
6) Supermale
7) Triploid (ovaries)
8) Triploid (testes)
9) X-Y tanslocation
10) Deletion of part of Y



What is SRY gene?

Sex determining region on Y chromosome
Encodes the SRY protein


What is the structure and mechanism of SRY protein?

SRY protein = 223 amino acids long

Contains a 79 amino acid HMG box

HMG box binds to DNA → ↑ SOX-9


What are the steps for fetal sexual differentiation?



What do sertoli cells secrete?

MIS (mullerian inhibitory substance)

MIS → ↓ paramesonephric duct (mullerian duct)


What do Leydig cells secrete?


Testosterone → ↑ mesonephric duct


What does the mesonephric duct become?

In males → Vas and associated ducts (epididymis and seminal vesicles)

In females → regresses


What does the paramesonephric duct become?

In males → regresses

In females → Fallopian tube, uterus and top of vagina


What 3 hormones, released from testis, act as gonadal-somatic messengers?

1) Androgens
- Stimulate development of penis, scrotum, vasa and accessory sex glands

2) Insulin like hormone 3
- Stimulate contraction of the gubernaculum → descent of testis

3) MIS
- Regression of paramesonephric duct (mullerian duct)


What is primary hermaphroditism?

- Can be ovary on one side + testes on other (rare)
- Can be mixed ovarian/testicular tissue in glands (XO/XY mosaicism)


What is secondary hermaphroditism?

1) Congenital adrenohyperplasia (CAH)

2) Androgen insufficiency syndrome (AIS)

3) 5-alpha reductase deficiency (guevodoces)

3) Micropenis

4) Hypospadias (urethra opens in ventral penis or in vagina)


What is Congenital adrenohyperplasia (CAH)?

Caused by deficiency in 21-hydroxylase (21-OHD)
- This is an enzyme needed for cortisol synthesis

21-OHD → ↓ cortisol secretion → ↑ ACTH (no -ve feedback)

↑ ACTH → ↑ cortisol precursors which are also precursors for androgens

This causes ↑ androgen secretion → in utero virilization of female genitalia


What is Androgen insufficiency syndrome (AIS)?

Genotype XY
Due to mutation in androgen receptor (AR) - 400 identified
Resistance to androgens → female appearance (range of different physical traits)
Normal testis (may not have descended)
Normal androgen production
No uterus/fallopian tube/upper vagina


What is 5-alpha reductase deficiency (guevodoces)?

5-alpha reductase is needed to make dihydrotestosterone
This condition have deficiency in external genitalia
XY but minimal virilisation at birth → extreme virilisation at puberty


Define Gender identity

An internal state of being

How people think of themselves and identify in terms of sex (man, woman, boy, girl)

Gender identity is a psychological quality
Consists of more than two categories:
(Space for those who identify as a third gender, both, or neither)
Many people feel that they have masculine and feminine aspects of their personalities


Define Gender stereotype or role

Socially expected attributes of men and women


Define Gender role

Everything we do that communicates our sex/gender to others


By what age is gender identity established?



By what age is gender role established (what age do children know what is expected of them)?



By what age do children realise that gender is fixed (gender consistency)?

5 yrs

It is at this stage that gender policing starts