Cell Cycle and Mitosis
• Cell cycle – steps that a cell goes through to grow and divide– 3 stages:
• Interphase – cell growth• Mitosis – nuclear division• Cytokinesis – cytoplasm division
http://www.cellsalive.com/cell_cycle.htm
Interphase
• “resting” phase• cell spends majority of
time in interphase– 3 parts:
• G1 – cell growth/metabolism
• S – DNA is copied• G2 – chromosomes start
to coil up
Mitosis# of Cells # of chromosomes per cell
Before Mitosis
After Mitosis
Phases of Mitosis
1. PROPHASE- nucleus disappears- chromosomes coil and are visible
Phases of Mitosis
2. METAPHASE- chromosomes line up in the middle of the cell along the equator
Phases of Mitosis
3. ANAPHASE- chromosomes split and are pulled to the opposite ends of cell
Phases of Mitosis
4. TELOPHASE- nuclei reappear- chromosomes uncoil- cell starts to pinch into 2 cells
Cytokinesis
Mitosis Revisited# of Cells # of chromosomes per cell
Before Mitosis 1 4
After Mitosis
In mitosis, one parent cell becomes two daughter cells with the same number of chromosomes as the parent cell.
http://www.cellsalive.com/mitosis.htm
In humans …
Why mitosis?
1. Asexual reproduction- many unicellular organisms use mitosis to make more of themselves
Why Mitosis?
2. To make more body cells in multicellular organisms- cells cannot get too big (nutrient demand)
Why Mitosis
- From one cell to adult
Why Mitosis
- To replace dead cells (ex. skin cells, blood cells, cheek cells)
- To replace damaged cells (ex. a cut healing)
http://www.schremppstudio.com/cutfinger.html
Onion Mitosis
Whitefish Mitosis
When Mitosis Goes Wrong
• Cell cycle is controlled by enzymes.
• When enzymes malfunction, there is uncontrolled mitosis.
• This can lead to cancer.
prostate cancer cells
cancer cells
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