Download Regulation of the Cell Cycle

Regulation of the Cell Cycle
In multicellular organisms, cells divide at different rates.
Cells in the intestine for example live only three days and must
be constantly replaced, whereas cells of the liver live for
more than a year. Brain cells on the other hand may never
reproduce.
The cell cycle can be regulated at any of the phases,
but typically, variability in the length of the cell cycle
is based on cells exiting the cell cycle at the G1 and G2
phases.
The tow phases of arrested growth are referred to as
“G0” and “G2 arrest”.
Mammalian cell growth is often studied in cultures
Cells stop growing when when there is no more surface area for them. This is called
Contact inhibition of growth, and the cells are said to have anchorage dependence.
Regulation of the Cell Cycle
Some cell lines lose the ability to control growth. These cell lines are referred to as transformed,
and they have become anchorage independent.
Mutations in two types of genes can cause this transformation:
Proto-oncogenes: These are genes associated with proteins that signal growth stimulation.
Tumor suppressor genes: These are genes associated with proteins that act as cell brakes that
inhibit cell proliferation.
Cancer
Cancer affects many aspects of cellular physiology/biology, but one of the major factors
involved is a loss of ability to control cellular proliferation.
Typically, about five independent mutations
are required to produce malignant cancer cells.
This is why older people are more likely to get
cancer.
Cancer
Potential causes:
1. mutations
2. retroviruses
3. exposure to DNA from transformed cells
4. heredity
5. any environmental factor that can induce 1, 2, and/or 3.
6. other