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