Download Cell Division

Cell
Division
We all start
out as a single
cell.
That single cell has:
•Cell membrane
•Cytoplasm and
organelles
That single cell has:
•Nucleus and a
nuclear
membrane
That single cell has:
•Chromatin
(chromosomes)
That single cell has:
•Centrioles
(only in animal
cells)
How do we
become our
multi-cellular
selves?
That first
single cell
must divide!
One becomes
two.
Two cells
become four.
Four becomes
eight.
Eight becomes
16.
16 becomes 32.
And so on.
The process of
cell division is
called mitosis.
It happens in
6 phases.
Phase 1
Interphase
Interphase: onion root
Interphase: animal cell
Interphase: plant cell
•Cell is
performing its
usual life
functions, and is
not dividing
•Chromosomes are
thin and threadlike (called
chromatin at this
stage)
•Near the end
of phase one,
the
chromosomes
are duplicated
•The
chromosome
count doubles
•The original and
copy
chromosomes are
attached at an
area called the
centromere
Phase 2
Prophase
Prophase: onion root
Prophase: animal cell
Prophase: plant cell
•The chromosomes
shorten and
become rod-like.
This makes them
stronger.
•The centrioles
move to
opposite ends
of the cell
•A mesh-like
bridge forms
between the
two centrioles
•In plants, the
bridge forms
without
centrioles
•The nuclear
membrane
breaks down
Phase 3
Metaphase
Metaphase: onion root
Metaphase: animal cell
Metaphase: plant cell
•The centromeres
attach the
chromosomes to
the mesh-like
bridge
Phase 4
Anaphase
Anaphase: onion root
Anaphase: animal cell
Anaphase: plant cell
•The centromere
splits, allowing the
chromosomes to
separate from
their copies
•The chromosomes
and the copies move
away from each
other on the meshlike bridge, toward
the centrioles
Phase 5
Telophase
Telophase: onion root
Telophase: animal cell
Telophase: plant cell
•The chromosomes
uncoil and
become threadlike chromatin
again
•A nuclear
membrane forms
around the
chromatin at each
end of the cell
Phase 6
Cytokinesis
Cytokinesis:
•The cell
membrane
pinches off
equal amounts
of cytoplasm
•Each part
contains a new
nucleus, and
there are two
new cells!
The end of
Cell Division!