REPRO - Genetics

Question 1

What does SRY transcription factor gene code for? When would it switch on..week.?

Answer 1

male pathway -> testes that make AMH & testosterone

week 7

Question 2

The bipotential gonads are derived from what?

At week..?

Answer 2

Common somatic mesenchymal tissue “the genital ridge primordia” around week 3/week 4

Question 3

What is the duct called that forms the: epididymus, vas deferans, prostate gland and seminal vesicles?

Answer 3

Wolffian/mesonephric

Question 4

What duct forms the uterus, fallopian tubes, cervix and upper 1/3rd of vagina?

Answer 4

Mullerian/paramesonephric duct

Question 5

What are the 3 waves of cells that invade the genital ridge?

Answer 5

• primordial germ cells (PGCs)
• primitive sex chords
• mesonephric cells

Question 6

PGCs begin as cell cluster in yolk sac epithelium than expand by mitosis (wk 3) then migrate to….

Answer 6

..CT of the hind gut -> genital ridge (colonised at wk 6)

Question 7

PGCs form..

Answer 7

• oocytes

- spermatoza

Question 8

The primitive sex chords are from the germinal epithelium that overlies the genital ridge then migrates.. and in men/women..

Answer 8

inwards as columns

• men: they penetrate the medulary mesenchyme, and surround PGCs forming testis cordis. Become sertoli cells.
• women: ill defined, dont penetrate, condense in cx as clusters around PGCs. Become granulosa cells.

Question 9

What do sertoli cells express?

Answer 9

AMH (Anti Mullerian Hormone)

Question 10

Where do mesonephric cells originate?

Answer 10

Mesonephric primordium (lat to genital ridge)

Question 11

Mesonephric cells in men vs women (make vascular tissue in both)?

Answer 11

Men: pre-sertoli cells and SRY…leydig cells make testosterone, the basement membrane helps to make semineferous tubules and rete testes
Women: Theca cells make adrostenedione, a substrate for E2 production from granulosa.

Question 12

If men..what about women:
PCG -> spermatoza
P. sex chords -> sertoli cells (AMH, SRY)
mesonephric cells -> Leydig cells (testosterone)

Answer 12

PCG -> oocytes
P. sex chords -> granulosa cells (E2)
mesonephric cells -> Theca cells (androstenedione)

Question 13

Where is testosterone converted to DHT (dihydrotestosterone) by enzyme…

Answer 13

in the genital skin, by 5a reductase

Question 14

DHT on the testosterone receptor causes differentiation of ext. male genitalia how?

Answer 14

• genital tubercle and urethral fold enlarges into penis

- genital swellings fuse and become ruggated into scrotum

Question 15

In females (with no DHT) what does the genital tubercle, swellings and urethral fold form?

Answer 15

• tubercle forms clitoris
• swellings form labia majora and minora
• urethral fold forms opening of vagina

Question 16

What is testosterone’s function?

Answer 16

-differentiation and growth of Wolffian duct structures (seminal vesicles, vas deferens…)

Question 17

What leads to the female external genitalia development?

Answer 17

Lack of androgens

Question 18

What is gonadal dysgenesis? Cause in male/female?

Answer 18

• incomplete sexual differentiation

- missing SRY in males, partial/full deletion of 2nd X in females

Question 19

what is sex reversal?

Answer 19

When phenotype doesnt match genotype

Question 20

What is intersex?

Answer 20

When components of both tracts are present or ambiguous genitalia

Question 21

Androgen Insensitivity Syndrome (AIS) 1/20,000 is due to androgen receptor issue. What happens is..

Answer 21

an XY individual appears female at birth

• they have SRY (make testis, make AMH)
• make testosterone & DHT but no receptors so Wolffian duct cant grow/no ext. male genitalia

Question 22

How may AIS present?

Answer 22

Primary Amenorrhoea, no body hair, undescended testes..NB they may feel female as brain has been exposed to only female signals

Question 23

Partial AIS has varying degrees of srotal/penile development, may be large clitoris..ambiguous..ajd at puberty..

Answer 23

..the large androgen surge can cause the appearence of male genitalia on the “female”

Question 24

5a reductase deficiency is normally A.Recessive condition when testosterone is made but no/little DHT so..
at puberty..

Answer 24

• XY, testis form, AMH, Wolffian ducts grow (int=male)
• no DHT (no ext male so ext=female/ambiguous)
• adrenarche testosterone may induce virilisation so “female” gets male ext genitalia

Question 25

Turner;s S. (XO) 1/3000, has 1 X due to maternal ovarian dysfunction. No SRY so no AMH, so wolffian regresses and ext=female but you get..

Answer 25

- "streak ovaries"/dysgenesis as we need both X for correct development - small uterus and tubes and defects in growth and development and infertile (unless mosaic)

Question 26

No 21-Hydroxylase means no cortisol and lack of neg feedback causes high CRH and ACTH. ACTH at adrenal cx... this is congenital adrenal hyperplasia

Answer 26

..more cholesterol uptake, side chain cleavage by p450s, more glucocorticoid secretions but more androgens as cortisol cant be made

Question 27

CAH is XX exposed to high androgens in utero, the completeness of the block varies, generally:

Answer 27

XX, no SRY, no testis, no sertoli, no AMH, ovaries form but CAH leads to more testosterone so wolffian and mullerian duct form (both int) and DHT leads to male ext.

Question 28

Lack of aldosterone in CAH can be lethal by | Whats given to correct feedback in CAH

Answer 28

"salt wasting" | -glucocorticoids

Question 29

Steroids are made from cholesterol which has: - #carbons - #six sided rings - #5 sided ring - with a

Answer 29

- #24 carbons - #3 six sided rings - # a 5 sided ring - with a tail

Question 30

Steroids are made by cutting off carbons of tail/switching groups - #21 carbons are - #19 carbons are - #18 carbons are

Answer 30

``` 21 = progestogens (e.g. progesterone, pregnenolone) 19 = androgens 18 = oestrogens ```

Question 31

What is Justice?

Answer 31

Acting in fairness, equal care for all

Question 32

Ethics. Non-maleficence (avoid unneccessary harm), Benefience (best interests), Justice and what?

Answer 32

Respect Autonomy - enable people to make their own reasoned informed choice

Question 33

What 3 steps can be taken if you have concerns that a situation is unethical?

Answer 33

- talk to your colleagues - document your discussions - contact the ethics committee if needed