development of the reproductive system and sex determination

Question 1

What is the name given to describe female gametes

Answer 1

homogametic

Question 2

what determines sex

Answer 2

the presence or absence of the Y chromosome

Question 3

describe the functions of the genes contained on the Y chromosome

Answer 3

contains a regulatory gene that control genes for testes development. Also contains genes unrelated to sex development.

Question 4

describe the genotype in XY females

Answer 4

part of the small arm of the Y chromosome is missing or mutated

Question 5

describe the genotype in XX males

Answer 5

they have a section of the Y chromosome translocated to an autosome or X chromosome

Question 6

what is the gene on the Y chromosome that determines sex

Answer 6

SRY

sex determining region of the Y chromosome

Question 7

what does SRY encode

Answer 7

a transcription factor that regulates expression of genes on other chromosomes responsible for testes

Question 8

What happens after gonadal differentiation

Answer 8

gonadal hormones are responsible for sexual dimorphism

Question 9

what two cell types form gonads

Answer 9

somatic mesenchyme and primordial germ cells

Question 10

what forms the genital ridge

Answer 10

proliferation of the surface epithelium and condensation of mesenchyme forming sex cords

Question 11

when do gonads differentiate

Answer 11

7th week

Question 12

what do primordial germ cells originate from

Answer 12

epiblast in the wall of the yolk sac

Question 13

where do primordial germ cells migrate to

Answer 13

genital ridge by chemotaxis and ameboid movement

Question 14

how many primordial germ cells are there

Answer 14

initially ten but they divide mitoticaly en route until there are about 2000

Question 15

when do the PGCs invade the genital ridges

Answer 15

6 weeks and then become surrounded by the primitive medullary sex cords

Question 16

what happens if PGCs fail to enter the genital ridge

Answer 16

gonads do not develop

Question 17

what do medullary sex cords go on to develop in the male

Answer 17

testes cords (medulla) and then rete testes (mesonephric cords)

Question 18

what do medullary sex cords go on to develop in the female

Answer 18

degenerate

Question 19

where do primordial germ cells come to reside in the male

Answer 19

testis cords

Question 20

what are sertoli cells derived from

Answer 20

mesoderm in the cords

Question 21

what do Leydig cells develop from

Answer 21

mesenchyme in interstitial spaces

Question 22

when do Leydig cells start producing testosterone

Answer 22

8 week

Question 23

what does testosterone do in the male foetus

Answer 23

influences the development of the genital ducts and external genitalia

Question 24

what does absence of a Y chromosome lead to

Answer 24

degeneration of primitive sex cords

Question 25

when do the second set of cords form in the female

Answer 25

12 weeks | from mesenchyme to form cortical cords

Question 26

what do the cortical cords do

Answer 26

surround each oogonium with epithelial follicular cells forming follicles

Question 27

when do the dual ductal systems form (forms internal genitalia)

Answer 27

7 weeks

Question 28

what ducts give rise to the male ductal system

Answer 28

mesonephric duct aka Wolffian

Question 29

what ducts give rise to the female ductal system

Answer 29

paramesonephric ducts aka Mullerian

Question 30

what other transcription factors are involved in differentiation of Sertoli and Leydig cells

Answer 30

SOX9 and SF1

Question 31

what hormone do sertoli cells express leading to regression of the Mullerian ducts and preventing development of female structures

Answer 31

AMH - anti mullerian hormone

Question 32

what do Leydig cells secrete in order to support development of the wolffian ducts and virilisation

Answer 32

testosterone

Question 33

what do mullerian ducts form in the absence of hormones

Answer 33

fallopian tubes

Question 34

what genes are involved in preventing maleness

Answer 34

WNT4 (ovary determing gene) up regulates DAX1 which inhibits the function of SOX9

Question 35

how does WNT4 promote female development

Answer 35

regulates genes responsible for ovarian differentiation

Question 36

what hormone simulates mullerian ducts to develop into femal internal genitalia

Answer 36

oestrogens

Question 37

what forms the lower vagina

Answer 37

paramesonephric tubercle aka sinovaginal bulb

Question 38

what forms the vagina plate

Answer 38

two evaginations growing out from the pelvic side

Question 39

when is vaginal outgrowth complete

Answer 39

20 weeks

Question 40

what is the genotype of turner's syndrome

Answer 40

45 X0

Question 41

describe the ovary in turner's syndrome

Answer 41

streak ovary as two X chromosomes are needed for full ovarian development

Question 42

what are the features of turner's syndrome

Answer 42

``` deficiency in ovarian steroids lack of secondary sex characteristics and infertility short stature webbed neck skeletal deformities and others ```

Question 43

what is genotype of Klinefelter's

Answer 43

47 XXY (44 autosomes)

Question 44

what are the features of Klinfelter's

Answer 44

male phenotype incomplete virilisation and breast enlargement small testes and fewer spermatogonia

Question 45

what is pseudohermaphroditism

Answer 45

gonads appropriate to their genotype but external genitalia of the opposite sex

Question 46

give an example of a pseudohermaphroditism

Answer 46

androgen insensitivity syndrome, 46 XY

Question 47

what are the features of androgen insensitivity syndrome

Answer 47

dysfunctional androgen receptor wolffian ducts degenerate female duct degenerate undescended testes

Question 48

what are the symptoms and signs of androgen insensitivity syndrome

Answer 48

``` appear female vagina may be short or blind ended sparse body hair infertile no menarche ```

Question 49

what is adrenogenital syndrome

Answer 49

congenital adrenal hyperplasia XX over active adrenal glands large amounts of steroid hormones which are androgenic development of wolffian ducts and male external genitalia female ducts also persist

Question 50

what structure is the precursor to the gonads

Answer 50

genital ridge

Question 51

what do cortical cords become

Answer 51

``` ovarian follicles (from mesenchyme) ```

Question 52

what do the medullary cords become

Answer 52

testis cords which then become the rete testis they secrete protein to nourish the sertoli cells

Question 53

what cell secretes AMH

Answer 53

sertoli cells