The Cell CycleChapter 6

What is it?

A repeating cycle of cell growth and division

Why do cells reproduce?

The Cell Cycle consist of three parts:

Interphase

This is the longest part of the cell cycle and is divided into three parts:

G1SG2

Interphase (part 1)

G1 (the first growth phase) – the cell graows rapidly in this phase and carries out its’ routine functions

Interphase (part 2)

S (synthesis phase) – in this phase, the DNA is copied

Why?

At the end of this phase, each chromosome consist of 2 chromatids

Why?

Interphase (part 3)

G2 (second growth phase) – in this phase, microtubules form in preparation of the actual division process

Microtubules will help move the chromosomes during cell division

Mitosis

This is the second part of the cell cycle and

This is where the cell actually divides. Think of it like cloning – the process ends up with two identical cells

Cytokinesis

This is the last part of the cell cycle and involves the cytoplasm dividing

Cell Cycle Control

How does a cell know when to divide?When not to divide?When to slow down ?

There are several “checkpoints” that let the cell know what to do

G1 checkpoint

If conditions are favorable for cell division (the cell is healthy, large enough), the cell will start the division process. If not, the cycle stops at the G1 stage.

Some nerve cells and muscle cells stay in this G1 stage forever… (think brain cells!)

G2 checkpoint

At this point the DNA has been copied, right? If the DNA looks good, mitosis will begin. If not, the cycle ends.

Mitosis checkpoint

After mitosis is complete, the cell will go back into the g1 stage (growth)

Cancer

Uncontrolled growth of cells

The gene for regulating cell growth and division is mutated

Questions:What is a tumor suppressing gene?What are the three types?

Your job

1. Read page 127 : Cancer2. Read page 128-132 to understand

the details of Mitosis3. Answer #’s 1-12 on page 1344. Illustrate the stages of mitosis on a

large poster board. Describe all the steps in detail. Make your drawings colorful, and make sure your illustration is labeled.

These will be due Tuesday November 29th