MitosisCh. 9.1-9.3

Objectives

1. Describe how cell reproduction contributes to repair and growth

2. Structure of a chromosome

3. Explain cell cycle

4. Understand mitosis and cytokinesis

5. Basics of cancer

Two Functions of Cells1. Repair

2. Growth• The outer layer of

skin on your arm consists of dead cell.

– Constantly replacing each other!

• Cells also key in reproduction . . . more on that later

An idea of where we’re at

The DNA• Genetic material

located in nucleus of cell

• Most of the time it exists as chromatin

• Chromatin:– Uncoiled DNA, not

visible

ChromosomesHome of the DNA

• Cell prepares to divide• Chromatin fibers

condense and become…• Chromosomes:

– Condensed, visible threads of genetic material

• Yarn example• Humans have 46

chromosomes

ChromosomesHome of the DNA

• Right before division, the cell duplicates all of it’s chromosomes

• Sister Chromatids:– Identical, joined copies

of chromosomes

• Centromere:– Joining region of

chromatids

Check Your Neighbor

• Quiz your neighbor on the terms we just learned.

The Cell Cycle

Let's Look at 3 examples of cell division (9.1 activity)

The Cell Cycle• All cells divide at

different rates• Interphase:

– 90% of cycle

• Three stages during interphase:

– G1

– Synthesis

– G2

• Miotic Stage (10%)

Cell CycleStages of Interphase

• G1:– Cell grows

• Synthesis:– DNA duplicates

• G2:– Cell prepares to divide

• Cell Cycle Animation and Different Types of Cells That Divide (9.2)

Cell Cycle Video Clip

Check Your Neighbor

• Quiz your neighbor on the cell cycle….

Mitosis• Mitosis:

– Non-sexual means of cellular reproduction

• Four Stages:1. Prophase2. Metaphase3. Anaphase4. Telophase• Cytokinesis

• Let’s use pipe cleaners to demonstrate the stages of mitosis. Draw them out after you make them.

MitosisProphase

• Nuclear envelope dissolves• Spindle forms• Chromosomes visible

MitosisMetaphase

• Chromosomes line up along equator• Spindles attach

MitosisAnaphase

• Chromatids separate• Pulled towards opposite ends of cell by spindles

MitosisTelophase

• Chromatids uncoil• Nuclear envelope re-forms

Cytokenesis• Division of cytoplasm• Two identical daughter cells• Mitosis: Let's watch the real thing!

Hand JiveProphase Metaphase

Anaphase Telophase

Mitosis Quiz

• When I pause the movie, you tell me what stage of Mitosis we are in.

Cancer• Family or friends with cancer?• Cancer:

– Uncontrollable cell division– Faulty checkpoints

• Out of control cell reproduction produces tumors

• Benign tumor: – Abnormal mass of normal cells

• Malignant tumor:– Mass of cancer cells

• Metastasis:– Spreading of cancer cells

Activity 9.4

More cancer animation

How a tumor is formed

Proto-oncogenes encourage cell division