sex determination

Question 1

what are the three parts to sex determinations

Answer 1

gonad formation, gonad determination, sex differentiation

Question 2

what does the nephrogenic ridge develop into

Answer 2

The nephrogenic ridge develops into the mesonephric ducts or Wolffian ducts and the precursors of the urinary system

Question 3

where does the Mullerian ducts arise from

Answer 3

The paramesonephric ducts or Mullerian ducts develop from further invagination of the intermediate mesoderm

Question 4

where do the primordial germ cells migrate to

Answer 4

gonandal ridge to devlop into gonads

Question 5

what gene drives testicular development in gonad determination

Answer 5

SRY expression, no sry and ovaries will be favoured in devlopment

Question 6

to achieve sex differentiation what aspects of body need to be affected by hormones

Answer 6

internal extra tissue for gonads, external gentalia, internal reproductive organs

Question 7

what regions of the x and y chromosome are the same

Answer 7

PAR1 and PAR2 on both ends of the chromosome

Question 8

where is sry gene located and why is this a risk for sry translocation

Answer 8

sry is close to par1 which can lineup with par 1 on x chromosome poor crossing over can mover sry gene to x chromosome

Question 9

what genes are important for teste formation

Answer 9

sry , sox9, dax 1

Question 10

where is dax 1 located and what does it do

Answer 10

DAX1 (orphan nuclear receptor) • Gene on X chromosome • Represses testes development • Dosage sensitive • duplications lead to DSD in XY individuals, male only has one x chromosome therefore one dax1 so teste not repressed enough andcan develop. (issue in kinefellter xxy)

Question 11

what does sox9 do

Answer 11

SOX9 • Gene on chromosome 17 • Acts on downstream targets to promote development of the testes • Dosage sensitive

Question 12

what evidence suggest that formation of the ovaries requires two x chromsomes and is not a passive process

Answer 12

For a long time formation of the ovary was thought to be a passive process • However, the observation that women with Turner syndrome (45, XO) do not develop functional ovaries suggested that some factor on the X chromosome was required

Question 13

what is the gonad called before gonad determination has occured

Answer 13

bi potential gonad because you can get testes or ovary

Question 14

what hormones are involved in sex differentiation of a male

Answer 14

amh and testosterone dht

Question 15

what does amh do in developing male

Answer 15

causes Mullerian duct regression

Question 16

what does testosterone do

Answer 16

Testosterone promotes the development of the Wolffian duct into the epididymis, vas deferens and seminal vesicles

Question 17

what does dht do

Answer 17

aggressive form of testosterone and drives external gentalia development

Question 18

what enzyme converts testosterone to dht

Answer 18

5 alpha reductase

Question 19

What are symptoms of 5 alpha reductase deficiency

Answer 19

Internal structures male • Variable appearance of external genitalia at birth • During puberty increased androgen levels lead to virilisation of external genitalia

Question 20

what is kinefellter and its symptoms

Answer 20

47XXY Normal at birth, higher incidence of undescended testes • Tall stature • Small ‘pea-sized’ testes • Lack of secondary sexual characteristics • Gynaecomastia • Infertility • Some behavioural and minor learning difficulties

Question 21

what does absence of AMH result in in female developing reproductive system

Answer 21

• The Mullerian duct develops into the fallopian tubes, uterus and upper vagina • The Wolffian duct regresses

Question 22

does the development of external genitalia in a female require

Answer 22

does not require functional ovaries a bit of a trick question, vagina clit and labia will form by default

Question 23

how can you treat sry translocation

Answer 23

testosterone