sex determination Flashcards
what are the three parts to sex determinations
gonad formation, gonad determination, sex differentiation
what does the nephrogenic ridge develop into
The nephrogenic ridge develops into the mesonephric ducts or Wolffian ducts and the precursors of the urinary system
where does the Mullerian ducts arise from
The paramesonephric ducts or Mullerian ducts develop from further invagination of the intermediate mesoderm
where do the primordial germ cells migrate to
gonandal ridge to devlop into gonads
what gene drives testicular development in gonad determination
SRY expression, no sry and ovaries will be favoured in devlopment
to achieve sex differentiation what aspects of body need to be affected by hormones
internal extra tissue for gonads, external gentalia, internal reproductive organs
what regions of the x and y chromosome are the same
PAR1 and PAR2 on both ends of the chromosome
where is sry gene located and why is this a risk for sry translocation
sry is close to par1 which can lineup with par 1 on x chromosome poor crossing over can mover sry gene to x chromosome
what genes are important for teste formation
sry , sox9, dax 1
where is dax 1 located and what does it do
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)
what does sox9 do
SOX9 • Gene on chromosome 17 • Acts on downstream targets to promote development of the testes • Dosage sensitive
what evidence suggest that formation of the ovaries requires two x chromsomes and is not a passive process
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
what is the gonad called before gonad determination has occured
bi potential gonad because you can get testes or ovary
what hormones are involved in sex differentiation of a male
amh and testosterone dht
what does amh do in developing male
causes Mullerian duct regression
what does testosterone do
Testosterone promotes the development of the Wolffian duct into the epididymis, vas deferens and seminal vesicles
what does dht do
aggressive form of testosterone and drives external gentalia development
what enzyme converts testosterone to dht
5 alpha reductase
What are symptoms of 5 alpha reductase deficiency
Internal structures male • Variable appearance of external genitalia at birth • During puberty increased androgen levels lead to virilisation of external genitalia
what is kinefellter and its symptoms
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
what does absence of AMH result in in female developing reproductive system
• The Mullerian duct develops into the fallopian tubes, uterus and upper vagina • The Wolffian duct regresses
does the development of external genitalia in a female require
does not require functional ovaries a bit of a trick question, vagina clit and labia will form by default
how can you treat sry translocation
testosterone
