Mitosis & Cancer:When Making New Cells

Goes Terribly Wrong!

When is mitosis a good thing?• When you have to add or replace cells– growth & development– repair– replacement

Controls on Growth

• The cell cycle is very carefully regulated, and there are two general ways that the growth of cell is limited:– External Factors– Internal Factors

External Factors

• Things that originate from outside the cell environment that regulate the cell cycle– Contact- cells in contact with other cells usually

stop dividing.– Growth factors- hormones and proteins that

stimulate or repress the growth of cells

Internal Factors

• Signals that originate from inside a cell to regulate the cell cycle– Cyclins- proteins that regulate the division of cells• May be involved with the timing of events in mitosis

– Genetic Controls- genes regulate when and how cells divide

Normal Control of the Cell Cycle

Proteins and enzymes control the cell cycle

• The cell cycle is controlled by proteins called cyclins and a set of enzymes that attach to the cyclin and become activated.

• Occasionally, cells lose control of the cell cycle.

Normal Control of the Cell Cycle

• uncontrolled dividing of cells can result from the failure to produce certain enzymes, the overproduction of enzymes, or the production of other enzymes at the wrong time.

• Cancer is a malignant growth resulting from uncontrolled cell division.– Cancer cells no longer respond to normal signals that

regulate division.

Cancer: A mistake in the Cell Cycle

• Currently, scientists consider cancer to be a result of changes in one or more of the genes that produce substances that are involved in controlling the cell cycle.

• Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients

When is mitosis a BAD thing

• Uncontrolled cell division is not good.• When cells reproduce & they are not needed

they can take over organs, but no longer function properly– they just keep making copies– This is cancer• damages organs

Growth of cancers

The causes of cancer• The causes of cancer are

difficult to pinpoint because both genetic and environmental factors are involved.

• Environmental factors, such as cigarette smoke, air and water pollution, and exposure to ultraviolet radiation from the sun, are all known to damage the genes that control the cell cycle. The factors are called carcinogens.

• Cancer may also be caused by viral infections that damage the genes.

Why would cells just make copies?

• Mutations: DNA gets damaged, cells stop listening to correct instructions, or lose the correct instructions.

• Causes of mutations (carcinogens): UV radiation chemical exposure radiation exposure heat

cigarette smoke pollution age genetics

Cancer: A mistake in the Cell Cycle

• In later stages, cancer cells enter the circulatory system and spread throughout the body, a process called metastasis, forming new tumors that disrupt the function of organs, organ systems, and ultimately, the organism.

Cancer prevention• Physicians and dietary experts

agree that diets low in fat and high in fiber content can reduce the risk of many kinds of cancer.

• Vitamins and minerals may also help prevent cancer.

• In addition to diet, other healthy choices such as daily exercise and not using tobacco also are known to reduce the risk of cancer.