Section 8.3
Control of the Cell Cycle
p. 211 - 213
Proteins and enzymes control the
cell cycle
• The cell cycle is controlled by proteins
called cyclins and a group of enzymes
that attach to them.
• Uncontrolled dividing may happen
because of not having the right
enzymes, too many enzymes, or
enzymes being made at the wrong time.
Cancer
• Is a growth resulting from uncontrolled
cell growth.
• This can be due to environmental factors
or changes in how many enzymes are
produced.
Enzyme production
• Genes control enzyme
production.
• Genes are located on
the chromosomes.
• A gene is a segment
of DNA that controls
protein production.
• Many scientists think that the end of G1
interphase is an important piece of the
puzzle as to why the signal gets messed
up.
• There are many enzymes that trigger
DNA replication.
Cancer: A Mistake in the Cell Cycle
• Comes from changes in one or more
genes that code for proteins involved with
the cell cycle.
• Many types of cancer form tumors.
• Some cancers like leukemia do not form
tumors.
Cancer: A Mistake in the Cell Cycle
• When cancer spread throughout the body
we call it metastasis.
• Cancers metastasize through the blood
and lymph systems.
• No matter where the cancer ends up, it is
named after the place it starts.
Cancer in the US
• Cancer is the second leading cause of
death in the US. (only heart disease kills
more people)
• It is estimated that 1/3 of all women and
½ of all men in the US will develop some
type of cancer.
• Lung, colon, breast, and prostate cancer
are the most prevalent types.
The causes of cancer
• The cause of cancer can be either
environmental or genetic.
• Environmental factors are noticeable when
groups from certain areas have a higher
incidence of cancer than other areas.
• Environmental factors from certain diets,
cigarette smoke, air and water pollution, uv
radiation from the sun are all known to damage
the genes that affect the cell cycle.
The causes of cancer
• Viruses also cause some cancers.
• In 2006 – Merck’s HPV vaccine, Gardasil,
was approved for use in the US to help
prevent cervical cancer.
Cervical cancer
• Normal cervical
cells as seen in a
Pap test
(above) contrast
with the
precancerous cells
(below) caused by a
persistent HPV
infection.
Human Prostate Cancer Cells
Human Breast Cancer Cells
Cancer Prevention
• Many studies indicate that there are links
between healthy life style choices and
cancer.
• Diets low in fat and high in fiber are
recommended to reduce the risk of
cancers.
• High fat diets have been linked to an
increased risk of colon, breast, and
prostate cancer.
Cancer Prevention
• Diets high in fiber are thought to reduce
the risk of colon cancer.
• Daily exercise and not smoking are also
strongly recommended in the task of
reducing the risk of cancer.
Colon cancer
A polyp is a growth that occurs in the colon and other organs.
These growths, or fleshy tumors, are shaped like a mushroom
or a dome-like button, and occur on the inside lining of the
colon.
While many colon polyps start out as benign (not harmful)
tumors, some polyps, in time, become malignant (harmful).
The larger the polyp, the more likely it is to contain cancer
cells.