ch 10 mitosis. cell growth limits to cell growth –why do cells divide? the larger a cell gets, the...

Ch 10 Mitosis

Cell Growth• Limits to Cell Growth

– Why do cells divide?•The larger a cell gets, the more

demands the cell puts on the DNA

Cell Growth

Before a cell gets too big, it divides forming two identical “daughter cells”

Cell Division• Every cell must copy its

DNA before cell division begins.

• Each daughter cell then gets a copy of that DNA

• In eukaryotes, cell division begins with the division of the nucleus called mitosis.

Chromosomes• Genetic information

is passed on by chromosomes

• Chromosomes are made of DNA

• Each chromosome is made of 2 sister chromatids and joined at the centromere.

Chromosomes

• When a cell is not in cell division, the DNA is found in the form of chromatin, not as chromosomes.

• DNA condenses to form chromosomes before cell division.

The Cell Cycle• During the cell cycle a

cell grows, prepares for division, and divides to form two daughter cells, each of which begins the cycle again.

• Interphase – Cell is preparing for division (G1, S, and G2 phase)

• AFTER Interphase, Mitosis begins. The daughter cells then enter Interphase. **CYCLE**

Cell Cycle Animation

Cell Cycle Animation p.2

Mitosis (PMAT)

• 1. Prophase• Chromosomes

condense and become visible

• Centrioles separate and get on opposite sides of the nucleus

•Centrioles help to organize the spindle fibers

**Mitosis occurs in Somatic Cells (body cells) when new cells are needed.**

Mitosis (PMAT)• 2. Metaphase

• Chromosomes line up across the center of the cell

Mitosis (PMAT)• 3. Anaphase

• The centromeres that holds the chromatids together split

• The spindle helps pull the pair of chromosomes apart

Mitosis (PMAT)• 4. Telophase

• Chromosomes gather at opposite ends of the cell

• Two new nuclear envelopes form

Mitosis

Uncontrolled Cell Growth• Cancerous

tumors are caused because cancer cells do not respond to the signals that regulate the growth of most cells.