Transcript Cell Cycle

Cell Cycle
Why do cells divide?
•
•
•
Growth
--by adding cells, not
having them get bigger
--cells are not efficient
for exchanging materials
if they are too big
--cells must have more
surface area than volume
Repair or Replacement
Reproduction
Three Steps in Cell Cycle
• Interphase- G1, S, and G2
– Cell grows and prepares for division
– 90% of time is spent in this phase for a cell
– Chromosomes copy themselves
• Mitosis- 4 steps of nuclear division
Prophase, Metaphase, Anaphase, Telophase
• Cytokinesis- division into two new cells
Mitosis
• Complex and delicate process
• 4 steps:
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–
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–
Prophase
Metaphase
Anaphase
Telophase
Prophase
• chromatin is developing
into chromatids
• cell membrane is
breaking down.
• Centrioles are moving
toward poles and
spindle fibers are
forming
Metaphase
• nuclear membrane
disappears.
• chromatids line up
on the metaphase
plate.
• spindle fibers are
connected to the
sister chromatids at
the centromere.
Anaphase
• the sister chromatids
separate by the pulling
action of the centrioles
on the spindle fibers.
Telophase
• The chromatids pulled
to poles.
• The nuclear membrane
is reforming
• A cell plate is
developing between
the two cells.
Cytokinesis
• Cytokinesis and telophase take place at approximately the
same time.
•Where mitosis is the division of the nucleus, cytokinesis is
the division of the cytoplasm.
•Once the division of the cytoplasm is complete, two new
cells have formed.
Answer the following questions
1. Is this an animal or a
plant?
2. What phase is this
slide in?
3. What helped you
determine which
phase this slide was
in?
Answer the following questions
4. Is this an animal or a
plant?
5. What phase is this
slide in?
6. What helped you
determine which
phase this slide was
in?
Answer the following questions
7. Is this an animal or a
plant?
8. What phase is this
slide in?
9. What helped you
determine which
phase this slide was
in?
Answer the following questions
10. Is this an animal or
a plant?
11. What phase is this
slide in?
12. What helped you
determine which
phase this slide was
in?
Answer the following questions
13. What phase is the
cell the arrow is on
in?
14. What phase is the
cell to the left of that
cell in?
15. Name the two
differences between
plant mitosis and
animal mitosis.