Sex determination

Question 1

where do gonads develop?

Answer 1

in the trunk of your body, halfway between shoulder and pelvis

Question 2

how do male and female embryos begin developing?

Answer 2

the same way, make the foundations for both sexes only differ when they start to make gonads

Question 3

where does the germ line come from?

Answer 3

epiblast cells that were removed from the body around the time of gastrulation, it therefore ends up outside the body in the yolk sac

Question 4

how does the germ line enter into the gonads?

Answer 4

the primordial germ cells invade the body via its connection with the yolk sac and the gut and its mesentery (sheet-like connection between the gut and the rest of the body)

Question 5

what determines sex?

Answer 5

SRY - agene on the Y chromosome

Question 6

how does SRY act?

Answer 6

primitive gonads consist of somatic and germ line cells
somatic cell express SRY if it is present
SRY forces somatic cells to develop into testis cells - otherwise they form ovaries

Question 7

how does the testis communicate with the rest of the body?

Answer 7

by excreting androgenic hormones
the rest of the body takes its cues from the testis

Question 8

sexual dimorphism in humans?

Answer 8

average height and mass
body shape
development of external genitalia
development of mammary glands
body hair pattern

Question 9

what does testosterone do?

Answer 9

stimulates androgen receptors weakly
5alpha-reductase converts it to 5alpha-dihydrotestosterone
5alpha-dihydrotestosterone is a strong stimulator of androgen receptors

Question 10

what are guevodoces?

Answer 10

people who are deficient in 5alpha-reductase
develop as a female up until they reach puberty when the increase in testosterone is enough to stimulate the androgen receptors