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Section 8.2
Cell Division
Binary fission –
cell division in prokaryotes
1.
2.
3.
DNA is copied  two molecules
New cell membrane forms
between the DNA molecules
Two identical cells are formed
Binary Fission
Cell division in eukaryotes



Two types of cell division:
Mitosis produces body cells
chromosome number stays diploid
Meiosis produces gametes – egg
or sperm
chromosome number is haploid
The Cell Cycle
1. Interphase –between cell divisions

G0 phase – cells stop dividing (nerve
cells)

G1 phase – growth

S phase – synthesis of DNA

G2 phase – get ready to divide
2. Cell division

Mitosis – organized separation of
chromosomes

Cytokinesis – division of the cytoplasm
Stages of Mitosis

1.
2.
3.
Prophase
Chromosomes appear
Nuclear envelope breaks down
Spindle fibers form

1.
Metaphase
Chromosomes in the middle of the
cell

1.
Anaphase
Chromatids separate at the
centromeres and are pulled toward
opposite ends of the cell

1.
2.
3.
Telophase
Chromosomes begin to change
back to chromatin
Nuclear envelope re-forms
Cytokinesis begins
Cytokinesis

1.
2.

1.
2.
In animal cells:
Cell membrane pinches in from
outside
Forms a cleavage furrow
In plant cells:
A cell plate forms in the middle of
the 2 cells
Cell wall grows across
Cytokinesis
Out of control

Cancer – caused by a mutation in
the genes that control cell division