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DO NOW:
How many chromosomes are in each of the four cells
below?
Binary Fission in Prokaryotes
1.
Chromosome copies
2.
Growth
3.
Division
Cell Cycle
Cell Cycle
The Life Cycle of a cell
Rate of Cell Cycle depends on the cell:
- Fast: embryo
- Fastest: skin, digestive tract
- Don’t divide: muscle (heart) and nerve (brain)
Interphase
-
First stage & longest of cell cycle
Nucleus and nucleolus clearly visible
Chromosomes not visible.
Not part of “Mitosis”
G1 = growth and activity
S = chromosomes copied
G2 = final preparations for cell division
G0 = do not copy or divide
Cell Division
• Stage of the cell cycle when the cell is
actually dividing.
• 2 stage process:
1. Mitosis – the nucleus divides and each
daughter cell is identical to the parent
cell
2. Cytokinesis – cytoplasm divides
The Four phases of Mitosis
PMAT
Prophase





chromatin condenses (chromosomes are now visible)
Chromosomes consist of two sister chromatids
nuclear membrane disappears
Centrosomes start to move to opposite ends (poles) of cell
Spindle fibers begin to form
 Kinetochore Fibers
 Polar Fibers
Metaphase

Spindles are fully formed

kinetochore fibers move
chromosomes to line up at the
center (equator) of the cell
Anaphase
• Sister chromatids separate
and move to opposite poles.
• Each chromatid is now
considered an individual
chromosome
Telophase

2 nuclear envelopes reform

Chromosomes uncoil into
chromatin

Spindles disappear
Cytokensis

cytoplasm is divided in half
 ANIMAL
PLANT 
Animation of Mitosis
1. Why does the nucleus enlarge during the S
phase?
2. If the cell meets all the criteria at each of its
checkpoints, it finally enters the M phase.
Describe what happens during this final
stage of the cell cycle.
3. Do all cells complete the cell cycle or go
through it at the same rate?