The Cell Cycle

A cell quest

I. Cell Cycle: Purpose

• A. The cell cycle is the cycle a cell goes through in order to make additional cells.1. Growth2. Replacing dead/worn-out cells3. Healing wounds

• B. The Stages of the cell cycle are 1. G1 (Gap 1)2. S (Synthesis)3. G2 (Gap 2)4. M (Mitosis)5. Cytokinesis

II. DNA Packing

Chromatin

Tightly coiled DNA contains genetic information

Holds sister chromatids together at the center

Loosely coiled DNA wrapped around histones

Two identical parts of a chromosome – “sister chromatids”

Cell Cycle Wheel

III. Interphase

• G1, S, and G2 are all part of interphase.• G1- During G1 the cell grows in size and collects all

the enzymes needed for Synthesis.• S- During Synthesis genetic information inside of the

cell doubles to create two sets of identical chromosomes. DNA replication– So if a cell normally has 23 pairs of chromosomes (like us!)

after S-phase it has 46 pairs.• G2- In G2, the cell produces microtubules, which are

needed for mitosis

III. Interphase

IV. Mitosis

• Mitosis is the division of one mother cell into two identical daughter cells.

• The phases of mitosis are prophase, metaphase, anaphase, and telophase.

A. Prophase

1. Spindle Fibers form2. Centrioles move to opposite poles 3. Chromosomes become visible

B. Metaphase

1. Chromosomes line up along the equator

C. Anaphase

1. Chromosomes divide2. Chromatids seperate and move to opposite

poles

D. Telophase

• Nuclear membrane forms around each group of chromosomes

• Chromosomes unwind• Cytokinesis begins

V. Cytokinesis

• The process by which the cytoplasm divides and one cell becomes two individual cells. The process is different in plants and animals

V. Cytokinesis

• Animals - cell membrane pinches inward

• Plants - a new cell wall forms between the two new cells

Cell Cycle Wheel

VI. What stops cell from growing?

A. Touching neighbor cells.– Cells in a petri dish will

continue to grow until they come into contact with other cells.

– Similarily, skin around a wound stops to grow when it contacts other skin cells

Which chemicals regulate the cell cycle?

• A protein called cyclin regulates the timing of the cell cycle and causes cells to divide.

How do cells respond to contact with other cells?

• Normally, cells stop growing when they come into contact with other cells

VII. How are cancer cells different from other cells?

• Cancer cells do not respond to cyclins that regulate the growth of most cells.

1. Cells divide uncontrollably and form masses of cells called tumors

2. The disease cancer results from these cells not performing their normal jobs

• Thought to be caused by a mutation on gene p53• p53 blocks cell maturation in damaged cells. • apoptosis

Lung Cancer

Oral cancer (tobacco chewing)

Cancer Treatment

• Surgery to remove cancer• Chemotherapy• Radiation• Viral Vector