Flashcards in 3.0 Sexual Differentiation Deck (23)
Why did evolution favour sex?
Recombination and allelic assortment helps to generate variation in populations (allows adaptation)
What determines gonadal 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
5) Klienfelter's syndrome
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?
- Stimulate development of penis, scrotum, vasa and accessory sex glands
2) Insulin like hormone 3
- Stimulate contraction of the gubernaculum → descent of testis
- 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)
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)?
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)?