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Module 5 Week 1 > Sex Determination And Development Of The Reproductive System > Flashcards

Sex Determination And Development Of The Reproductive System Flashcards

1
Q

True or false, males and females are identical before sex determination. If true what’s this stage called

A

True-> indifferent gonad

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2
Q

Process of Sex determination of males

A

Indifferent gonad—> (action of y Chromosome gene) —>testis—> male phenotype

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3
Q

Process of female sex determination

A

Indifferent gonad—> (absence of Y chromosome)—> ovary—> female phenotype

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4
Q

Gene on Y chromosome that induces testis formation called

A

Sex determining Region on the Y chromsome (SRY) (only found on Y chromosome)

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5
Q

2 main genes involved in normal determination of sex

A

SOX9 and FOXL2

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6
Q

Describe the pathway of sex determination involving inhibition of SOX9.

A

Either Wnt4 promotes beta-catenin which inhibits SOX9 causing indifferent gonad to turn into ovary
Or FOXL2 inhibits SOX9 and causes the same thing

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7
Q

Describe the pathway of sex determination that promotes SOX9

A

WT1, FOG2, GATA4 promotes the SRY gene which promotes SOX9 causing indifferent gonad to turn into testis

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8
Q

Sex determination in birds
-what are the sex chromosomes and which pattern is in male and female

A

-Z AND W
-Male is homogametic ZZ
-female is heterogametic ZW

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9
Q

What controls the reptiles and amphibians sex since many have no sex chromsome

A

Temperature of egg—>

Cool nest=female offspring
Warm nest=male offspring

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10
Q

What are the 3 pairs of kidney sets formed during development of reproductive system

A

Pronephros
Mesonephros
Metanephros

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11
Q

Which kidney Pair does the gonad develop in?

A

Mesonephros

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12
Q

Describe each step of reproductive system development

A

On anki

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13
Q

Name the cells that form mature follicles in ovary and sperm in testis

A

Primordial germ cells

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14
Q

Are primordial or gonad cells first in development?

A

Primordial germ cells

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15
Q

True or false primordial cells aren’t found in gonad cells but need to migrate there

A

True

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16
Q

Describe the steps of testis development; once the germ cells has reached gonad

A
  1. Germ cells enter gonad
  2. Coelomic epithelial cells invade indifferent gonad and become Sertoli cells
  3. Form sex cords
  4. Germ cells enter sex cords
  5. Sex cords “detach” to form seminiferous tubules
  6. Paramesonephric duct degenerates
  7. Mesonephric duct persists

(On anki cards too with diagrams)

17
Q

What happens differently in females during ovary development?

A

Since there is no Y chromosome, coelomic epithelium does not invade to form Sertoli cells; no invasion to form sex cords
Instead germ cells form oocyte nests which go on to form primordial follicles some time before birth
Also in female its the paramesonephric duct that persists and mesonephric duct that degenerates

18
Q

What happens to germ cells throughout life in females

A

Proliferate then enter meiosis but halt at diplotene until after puberty
Total number of germ cells decreases throughout life even before birth/at birth

19
Q

What happens to germ cells throughout life in males

A

Limited proliferation in early development, and do not enter meiosis until puberty, something inhibits this. Massive proliferation after puberty

20
Q

Why does meiosis not occur in males during life of germ cells

A

Enzyme cyp26b1. Inhibits vitamin A and stops them from entering meiosis. (Need vit A to enter like in females)

21
Q

Name the reproductive duct systems

A

Paramesonephric (female) and mesonephric duct (male)

22
Q

What does the paramesonephric duct form

A

Uterine tubes, horns, body
Cervix
Cranial vagina

23
Q

What does the mesonephric duct form

A

Epididymis
Ductus deferens

24
Q

What controls formation/degeneration of male/female tract

A

The presence or absence of testis

25
Q

What occurs to the duct in presence of testis

A

Either: testosterone secreted—> stabilises mesonephric duct which is inherently unstable—> male tract formed
Or: testosterone produces AMH—>causes stable paramesonephric duct to degenerate—> no female tract formed

26
Q

What occurs to the duct in absence of testis

A

Either: there no testosterone as no testes present—> unstable mesonephric duct degenerates—> male tract not formed
Or: no AMH present as no testes present: stable paramesonephric duct persists—>female tract formed

27
Q

What controls development of external genitalia

A

Testis once again; presence or absence of androgen

28
Q

What occurs to the external genitalia in a female

A

No androgen present; urogenital (UG) orifice remains open so GT forms clitoris

29
Q

What occurs to the external genitalia in male

A

Androgen present; UG folds fuse to close UG orifice
GT forms penis. Urethra extends along to distal end of GT

30
Q

What enzyme is required to turn testosterone into DHT to then promote action of androgen to masculinise external genitalia in a male

A

5a-reductase

(a=alpha)

31
Q

What happens to a female who has been exposed to androgen?

A

Female becomes androgenised; forms ovaries, empty scrotum and a penis

32
Q

What condition occurs in males when there is lack of androgen?

A

Get a condition called hypospadias; genital condition in males in which opening of urethra forms abnormally (usually found at top but can form half way up

33
Q

What is bovine freemartin and what is it caused by

A

Dizygotic bovine twins of opposite sex (2-10% twinning rate)

Caused by placental fusion which leads to blood mixing
Factors released from testes in XY twin that gets into XX female and therefore components that are not normally present in female can masculinise it; 95% will be infertile due to this

34
Q

What happens during male development:
-if androgen receptors were non-functional
-5a-reductase faulty

A

Testes would form normally (Y chromosome) and secrete T and AMH
But T and DHT could not act
So internally both mesonephric and paramesonephric ducts would degenerate Externally the phenotype would not masculinise
Result is external female phenotype

Failure to make DHT
Internally the normal male ducts would develop but externally the individual would appear female at birth
At puberty massive rise in testosterone which causes growth of penis and pubertal masculinisation

Module 5 Week 1 (14 decks)

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