Gametogenesis
Oogenesis
or
Spermatogenesis
1
Spermatogenesis
Occurs in the
testes
Two divisions
produce 4
spermatids
Spermatids mature
into sperm
Men produce about
250,000,000
sperm per day
2
Spermatogenesis in the Testes
Spermatid
3
Spermatogenesis
4
Oogenesis
Occurs in the ovaries
Two divisions produce 3 polar bodies
that die and 1 egg
Polar bodies die because of unequal
division of cytoplasm
Immature egg called oocyte
Starting at puberty, one oocyte
matures into an ovum (egg) every 28
days
5
Oogenesis in the Ovaries
6
Oogenesis
First polar body
may divide
(haploid)
a
X
a
a
X
a
Mitosis
Oogonium
(diploid)
A
X
X
Primary
oocyte
(diploid)
Polar
bodies
die
X
Meiosis I Meiosis II
(if fertilization
occurs)
A
X
A
X
Secondary
oocyte
(haploid)
Ovum (egg)
A
Mature
egg
X
Second
polar body
(haploid)
7
Comparing Mitosis
and Meiosis
8
Comparison of Divisions
Mitosis
Meiosis
2
Number of
divisions
1
Number of
daughter cells
2
4
Yes
No
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Growth and
repair
Sexual reproduction
9
Genetically
identical?
Chromosome #
Role