Control of sex determination

Question 1

What gene controls testicular differentiation

Answer 1

SRY expression

Question 2

What embryological ducts lead to the production of male reproductive organs?

Answer 2

Wolffian ducts

Question 3

What embryological ducts lead to the production of female reproductive organs?

Answer 3

Mullerian ducts

Question 4

What role does SOX9 play in gonad development?

Answer 4

Gene on chromosome 17; acts on downstream targets to promote development of testes.

Question 5

What role does DAX1 play in gonad development?

Answer 5

Gene on X chromosome, represses testes develpoment - dosage sensitive, and duplications therefore lead to DSD in XY individuals

Question 6

How do gonads become testes?

Answer 6

AMH (anti mullerian hormone) leads to regression of mullerian structures.
Testosterone promotes the development of the wolffian ducts into the epididymis, vas deferense and seminal vesicles

Question 7

What androgen is important in the formation of the external genitals in male

Answer 7

Dihydrotestosterone - causes formation of penis, scrotum and prostate

Question 8

How does the female internal genetalia develop in the embryo?

Answer 8

The mullerian duct develops into the fallopian tubes, uterus and upper vagina; the Wolffian duct regresses

Question 9

What are the symptoms of Klinefelter syndrome

Answer 9

XXY

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