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Mrs. Crouch
Biology 1 Honors
the Cell Cycle
The Cell Cycle
& Mitosis
•A period of time from the
beginning of one cell division to the
beginning of the next cell division.
G1 Phase
M Phase
S Phase
•Divided into 4 phases
(G1, S, G2, and M)
G2 Phase
Interphase
Cell Cycle
Mitosis
G1 Phase
•Growth & activity
•Cell double in size
•Number of ribosomes &
mitochondria double
S Phase
•Chromosome replication
•DNA molecules duplicate
G2 Phase
•Final preparation for division
•Spindle fibers assemble
Mitosis
•Actual cell division
• The process of nuclear division in
eukaryotic cells.
• Prokaryotic cells
undergo a similar
process called binary
fission
4 Phases of Mitosis
Chromosome
Chromosome • has 2 coiled chromatids, joined at the
centromere
Chromatid • Single strand of a chromosome
• Found in identical pairs
• Called “sister chromatids”
Centromere
• Part of the chromosome where the
chromatids are attached
Prophase
•Longest phase (60%)
Chromatid
Centromere
Prophase
Metaphase
Anaphase
Telophase
•Chromosomes come together and form
thick thread like structures
•Centrioles separate (in animal cells only)
•Spindle fibers grow from the centrioles
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Mrs. Crouch
Biology 1 Honors
Metaphase
Anaphase
•Shortest phase
•Centromeres holding the chromatids
split
•Chromosomes are completely attached
to spindle fibers
•Microtubules pull the chromatids apart
•Chromosomes line up in the center of
the cell
•Chromosomes (single stranded) are
now at two separate ends
Cytokinesis
After cytokinesis, the daughter cells
return to interphase
Telophase
•Spindle fiber begins to break apart
•Chromosomes at each end of the cell,
start to spread out
•Nuclear membranes form around each
cluster of chromosomes
- Two distinct nuclei are formed
within the cell
Mitosis (Onion Cell)
•Cytoplasm and it’s contents divide into
2 daughter cells
•Each daughter cell receives 1 nucleus
and half of the cytoplasm & organelles
Cell Cycle and Cell Division Facts
Questions? Comments?
Mouse Cell - completes the cell cycle in 22 hours
Bean Cell - completes the cell cycle in 19 hours
Adult Human -Around 2 trillion cell divisions
occur in a 24 hour period
* This = 25 million cell divisions per second!
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