Transcript Meiosis

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Meiosis
Chapter 8
Baby/Zygote
Meiosis I
 Meiosis
is cell division but one step
further, it reduces the material by half and
makes a total of four cells when it is
finished. This only happens in the sex
cells of an organism. If an organism is not
a sexual organism and reproduces by
itself then this never takes place in that
organism at all.
Meiosis I
 Interphase
I cell rests and grows
 Prophase I doubles all material
tetrad – pair of doubled, matching
chromosomes. Here is where there is
crossing over of traits and more Variety
appears.
 Metaphase I all the genetic material lines
up in the center of the cell, and cell
structures to one side or the other.
Meiosis I
 Anaphase
I Action stage where the
materials pull apart to the poles of the cell
this creates independent assortment.
 Telophase
I and Cytokinesis I the cell
pinches in and starts to clump material into
the nucleus, new cell membrane forms.
Meiosis II (x 2)
 Prophase
II
Nuclear membrane
disappears and the material in the cell
organizes
 Metaphase II
The chromosomes line
up and the spindle fibers attach to both
chromatids.
 Anaphase II
This is where the
reduction division takes place. Each
chromosome will divide in half, and pull
apart.
Meiosis II
 Telophase
II
Cell pinching-in takes
place in each of the four cells. The new
cell membrane forms and all material is
moved to a new nucleus. Resulting in four
new cells.
 Gametes
Four new sex cells of
gametes are formed and each has half of
the first cells material and genetic
information. Sperm and Eggs
Gametes
– one cell makes four sperm and
are functioning and able to fertilize an egg
 Egg (ova) – only one ova is able to be
fertilized the other three cells will be
smaller and will be called polar bodies and
in most cases will never be able to get
fertilized.
 Sperm
Watch it take place…
 Meiosis
 Meiosis
again