Sex Determination And Development Of The Reproductive System

Question 1

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

Answer 1

True-> indifferent gonad

Question 2

Process of Sex determination of males

Answer 2

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

Question 3

Process of female sex determination

Answer 3

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

Question 4

Gene on Y chromosome that induces testis formation called

Answer 4

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

Question 5

2 main genes involved in normal determination of sex

Answer 5

SOX9 and FOXL2

Question 6

Describe the pathway of sex determination involving inhibition of SOX9.

Answer 6

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

Question 7

Describe the pathway of sex determination that promotes SOX9

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

Temperature of egg—>

Cool nest=female offspring
Warm nest=male offspring

Question 10

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

Answer 10

Pronephros
Mesonephros
Metanephros

Question 11

Which kidney Pair does the gonad develop in?

Answer 11

Mesonephros

Question 12

Describe each step of reproductive system development

Answer 12

On anki

Question 13

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

Answer 13

Primordial germ cells

Question 14

Are primordial or gonad cells first in development?

Answer 14

Primordial germ cells

Question 15

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

Answer 15

True

Question 16

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

Answer 16

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)

Question 17

What happens differently in females during ovary development?

Answer 17

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

Question 18

What happens to germ cells throughout life in females

Answer 18

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

Question 19

What happens to germ cells throughout life in males

Answer 19

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

Question 20

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

Answer 20

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

Question 21

Name the reproductive duct systems

Answer 21

Paramesonephric (female) and mesonephric duct (male)

Question 22

What does the paramesonephric duct form

Answer 22

Uterine tubes, horns, body
Cervix
Cranial vagina

Question 23

What does the mesonephric duct form

Answer 23

Epididymis
Ductus deferens

Question 24

What controls formation/degeneration of male/female tract

Answer 24

The presence or absence of testis

Question 25

What occurs to the duct in presence of testis

Answer 25

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

Question 26

What occurs to the duct in absence of testis

Answer 26

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

Question 27

What controls development of external genitalia

Answer 27

Testis once again; presence or absence of androgen

Question 28

What occurs to the external genitalia in a female

Answer 28

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

Question 29

What occurs to the external genitalia in male

Answer 29

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

Question 30

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

Answer 30

5a-reductase (a=alpha)

Question 31

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

Answer 31

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

Question 32

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

Answer 32

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

Question 33

What is bovine freemartin and what is it caused by

Answer 33

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

Question 34

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

Answer 34

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