Male vs. Female
Meiosis
Gametogenesis
Remember that during meiosis, the goal is to
create sex cells (gametes)
This process is a bit different in males and
females
Re-cap
In the reproduction unit we learned that gamete
production in males is called spermatogenesis
and the end result is sperm.
In females, it is called oogenesis and the end
result is an egg.
Spermatogenesis
During meiosis in males, spermatogenesis occurs in the
seminiferous tubules in the testes.
The spermatocyte has 46 chromosomes.
These become spermatid which have 23 chromosomes.
These then become sperm which also have 23
chromosomes.
Draw me:
As you can
see, there are
four gametes
produced
during this
meiotic
division
Oogenesis
During meiosis in females, oogenesis occurs in the
ovaries.
The primary oocyte has 46 chromosomes.
This becomes the secondary oocyte which has 23
chromosomes and the first polar body.
The secondary oocyte then splits into the ovum and the
second polar body. The polar body also divides to
become two more polar bodies. These polar bodies then
die due to lack of cytoplasm and nutrients.
Draw me:
As you can see,
there is only one
gamete produced
in females and
three cells that die.
This is how only
one egg is
produced at a time.
Comparing the Gametes
The diploid cells that give rise to sperm (spermatogonia)
are capable of many mitotic divisions before meiosis
begins.
Males can make as many as one billion sperm every day
once they reach puberty.
Females are born with approximately 2 million primary
oocytes which have already entered meiosis I but they
remain in prophase I until puberty. Meiosis resumes in
one oocyte at a time every month.
What about Twins?
As stated above, only one egg should be produced during
meiosis in females.
This isn’t always the case though.
There are three types of twins that can occur and they
each have a scientific name. Using page 565 and the
computers, you will be completing an activity to explore
these cases.