Genital Development Slide Show

1
The Y Chromosome
Why has the Y chromosome been important for the
development and evolution of vertebrates?
2
Determination of Gonadal Sex
Human
Mouse
Ovary
Ovary
XX
Streak
Ovary
X0
Testis
Testis
XY
XXY
Testis
Testis
The presence or absence of the Y chromosome
determines the sex of the gonad.
3
The Sex Chromosomes
X
Y
p
p
q
heterochromatin
q
4
Karyotype of a Human Male
?
46, XX male
5
Molecular Detection of Y Chromosomal DNA
?
?
XX ?
6
The Sex Chromosomes
X
Y
p
p
q
q
7
Mechanisms for Transferring Y DNA to the X
Chromosome
8
(No Transcript)
9
Transgenic Mice
Introduction of SRY into the female genome at the
zygotic stage results in the development of
testes and the male phenotype in mice.
10
Indifferent Gonad
TDF
-TDF
All gonads start out indifferent, i.e.the same in
both the male and female.
11
Migration of Germ Cells into the Gonadal Ridge
Gonadal
Gonadal
12
Stabilization of Primary Sex Cords
13
Degeneration of Primary Sex Cords
14
Sex Determination Versus Sex Differentiation
15
Dual Plumbing
Internal genitalia for both sexes coexist in the
early stages of genital development.
16
Development of Internal Genitalia
17
Development of Internal Genitalia

The gonadal hormones testosterone and MIS (a.k.a.
AMH) direct the masculinization of internal
genitalia when a testis is present.
18
Development of Internal Genitalia
Mesonephric duct
Paramesonephric duct
Gonad
19
Development of External Genitalia
The external genitalia starts out identically in
males and females (i.e. indifferent).
20
Development of External Genitalia
21
Development of External Genitalia
The indifferent external genitalia can become
either male or female depending on the presence
or absence of a testis.
22
Development of Male External Genitalia
Normally, the presence of a testis masculinizes
the external genitalia.
23
Development of Female External Genitalia
The absence of a testis feminizes the external
genitalia .
24
The Role of Androgen
5a-Reductase Deficiency
5a-Reductase
Testosterone DHT