Cell Growth

and Division

I. Background Info A. Chromosomes

1. Carry all the genetic information (DNA) for an organism.

2. Made of chromatin.a) Chromatin is made

of DNA twisted around a protein called histone.

3. Involved in cell growth and division

B. Why Do Cells Divide?

1. Growth of an organism

2. Replace dead or damaged cells

3. Reproduction in single-celled organisms

4. Prevent “DNA overload”

C. Why don’t cells keep getting bigger and bigger as an organism grows?

1. Cell membrane can’t handle the flow of materials

2. Nucleus can’t control the functions of a large cell

3. Raw materials and waste could not get in or out of the cell fast enough

4. So a cell divides into two new cells that are identical to the original

II. The Cell CycleA. Cell cycle is a series of events that takes place from

one cell division to the next

B. The time it takes to complete a cell cycle is different for every type of cell

C. Consists of Interphase , Mitosis (cell division), and Cytokinesis

Cell Cycle Movie

1. Interphasea. The cell is performing life functions, but

not actually dividing.b. Chromosomes are not visible.

c. Consists of 3 phases:1) G1 (1st growing phase) - cell growth; right

after cell division.2) S (synthesis phase) - DNA replication

(copying)3) G2 (2nd growing phase) - replication of cell

organelles (to prepare for division) and synthesis of cell division structures.

G2 phase

S phase

G1 phase

Interphase Movie

Bill Nye Mitosis Movie

III. Stages of Mitosis

A. Prophase

1. Nuclear membrane & nucleolus start to disappear

2. Spindle fibers and centrioles appear

3. Chromosomes are visible

Prophase Movie

B. Metaphase

1. Chromosomes line up at the center of the cell (metaphase plate) by attaching themselves to the visible spindle fibers

Metaphase Movie

C. Anaphase

1. The chromosomes are pulled (at the centromeres) to the opposite poles of the cell.

2. Each chromosome now is a single chromatid.

3. Each side gets an exact copy of each chromosome

Anaphase Movie

D. Telophase

1. Nuclear membrane and nucleolus reappears.

2. Chromosomes and spindle fibers start to disappear.

3. Mitosis is complete at this point.

Telophase Movie

IV. Cytokinesis

A. Cytokinesis is the division of organelles and cytoplasm

B. Two IDENTICAL daughter cells are formedC. In plant cells the Golgi bodies secrete a cell

plate in the middle of the cell.

Cell Plate

Cell Division Quiz Movie

A. Cancer is the result of uncontrolled cell division.

B. Can form masses of cells called tumorsC. If a cancer cell breaks loose from a tumor, it can

spread to other parts of the body (metastasize)D. Causes:

1. Tobacco2. Alcohol3. Viruses (HPV)4. Radiation (sun, radioactive materials)

V. Cancer

VI. Stem CellsA. Three to five days after fertilization, a

human embryo is a mass of cells called stem cells

B. Stem cells are have the ability to develop into any type of specialized cell (differentiation)

Stem Cell Movie