Development of sexual characteristics Flashcards
What is the SRY gene?
‘Sex-determining region Y’
A gene carried on the Y chromosome that causes testes to develop in an XY embryo.
The testes then produce androgens which cause the embryo to be male.
What does MIF stand for? What is it?
Mullerian inhibiting factor
It inhibits the development of Mullerian ducts in a male embryo
What are the Mullerian and Wolffian ducts?
Embryonic structures that precede adult sexual organs.
Describe what actually happens with Mullerian and Wolffian ducts in males!
Both develop as an embryo develops
If a Y chromosome is present, SRY gene will be present and testes will have developed
Testes release MIF - a hormone that causes regression of Mullerian duct
So no female genitalia develop
Describe what actually happens with Mullerian and Wolffian ducts in females!
Both ducts develop as the embryo develops
No Y chromosome = no SRY gene = no testes
No testes = no MIF
Mullerian duct does not regress and forms female genitalia
Wolffian duct regresses
What is dihydrotestosterone?
An androgen
A hormone that stimulates development of male characteristics
How is dihydrotestosterone made?
Conversion of testosterone by the testes & prostate in men and the ovaries in women
In terms of dihydrotestosterone, how is the onset of puberty stimulated?
An increase in the rate of conversion of testosterone into dihydrotestosterone causes the onset of puberty
What are primary sexual characteristics?
The sexual characteristics a person is born with
What are secondary sexual characteristics?
Sex characteristics that develop later in life, usually during puberty
Give some examples of primary sex characteristics.
Presence of gonads, sex hormones, internal and external genitalia
Give some examples of secondary sex characteristics.
Breasts, menstrual cycle, facial and body hair
