3.0 Sexual Differentiation Flashcards
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<br></br><br></br>This is done through <b>messengers</b><br></br>- Can be paracrine peptide molecules<br></br>- Or endocrine molecules
What is the autosomal number, sex chromosomes and gonads present for the following conditions:<br></br>1) Turner’s syndrome<br></br>2) Female<br></br>3) Superfemale<br></br>4) Male<br></br>5) Klienfelter’s syndrome<br></br>6) Supermale<br></br>7) Triploid (ovaries)<br></br>8) Triploid (testes)<br></br>9) X-Y tanslocation<br></br>10) Deletion of part of Y
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What is SRY gene?
Sex determining region on Y chromosome<br></br>Encodes the SRY protein
What is the structure and mechanism of SRY protein?
SRY protein = 223 amino acids long<br></br><br></br>Contains a 79 amino acid <b>HMG box</b><br></br><br></br>HMG box binds to DNA → ↑ <b>SOX-9</b>
What are the steps for fetal sexual differentiation?
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What do sertoli cells secrete?
<b>MIS (mullerian inhibitory substance)</b><br></br><br></br>MIS → ↓ paramesonephric duct (mullerian duct)
What do Leydig cells secrete?
<b>Testosterone</b><br></br><br></br>Testosterone → ↑ mesonephric duct
What does the mesonephric duct become?
In males → Vas and associated ducts (epididymis and seminal vesicles)<br></br><br></br>In females → regresses
What does the paramesonephric duct become?
In males → regresses<br></br><br></br>In females → Fallopian tube, uterus and top of vagina
What 3 hormones, released from testis, act as gonadal-somatic messengers?
<b>1) Androgens</b><br></br>- Stimulate development of penis, scrotum, vasa and accessory sex glands<br></br><br></br><b>2) Insulin like hormone 3</b><br></br>- Stimulate contraction of the gubernaculum → descent of testis<br></br><br></br><b>3) MIS</b><br></br>- Regression of paramesonephric duct (mullerian duct)
What is primary hermaphroditism?
- Can be ovary on one side + testes on other (rare)<br></br>- Can be mixed ovarian/testicular tissue in glands (XO/XY mosaicism)
What is secondary hermaphroditism?
1) Congenital adrenohyperplasia (CAH)<br></br><br></br>2) Androgen insufficiency syndrome (AIS)<br></br><br></br>3) 5-alpha reductase deficiency (guevodoces)<br></br><br></br>3) Micropenis<br></br><br></br>4) Hypospadias (urethra opens in ventral penis or in vagina)
What is Congenital adrenohyperplasia (CAH)?
<b>Caused by deficiency in 21-hydroxylase (21-OHD)</b><br></br>- This is an enzyme needed for cortisol synthesis<br></br><br></br>21-OHD → ↓ cortisol secretion → ↑ ACTH (no -ve feedback)<br></br><br></br>↑ ACTH → ↑ cortisol precursors which are also precursors for androgens<br></br><br></br>This causes ↑ androgen secretion → in utero <b>virilization</b> of female genitalia
What is Androgen insufficiency syndrome (AIS)?
<b>Genotype XY</b><br></br><b>Due to mutation in androgen receptor (AR)</b> - 400 identified<br></br><b>Resistance to androgens → female appearance</b> (range of different physical traits)<br></br><b>Normal testis</b> (may not have descended)<br></br><b>Normal androgen production</b><br></br><b>No uterus/fallopian tube/upper vagina</b>
What is 5-alpha reductase deficiency (guevodoces)?
5-alpha reductase is needed to make dihydrotestosterone<br></br>This condition have deficiency in external genitalia<br></br>XY but minimal virilisation at birth → extreme virilisation at puberty
Define Gender identity
An internal state of being<br></br><br></br>How people think of themselves and identify in terms of sex (man, woman, boy, girl)<br></br><br></br>Gender identity is a psychological quality <br></br>Consists of more than two categories:<br></br>(Space for those who identify as a third gender, both, or neither)<br></br>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?
2yrs
By what age is gender role established (what age do children know what is expected of them)?
2-3yrs
By what age do children realise that gender is fixed (gender consistency)?
5 yrs<br></br><br></br>It is at this stage that gender policing starts
