Download Cancer: A mistake in the Cell Cycle

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):
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UV radiation
chemical exposure
radiation exposure
heat
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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.