|
Scientists have discovered
that some cells have a natural tendency to become cancerous
on their own because they contain certain genes that could
cause cancer.
Some cells are normal
at first because they contain genes called Tumour-suppressor
genes. They stop cells from growing abnormally into a tumour.
When these Tumour suppressor genes are inactivated
or destroyed completely by carcinogens, they lose their `braking
power' and allow the cells to divide abnormally instead of
stopping them.
Other cells have genes
called Oncogenes (onco- means `cancer'). In
a normal cell, these oncogenes help to regulate normal cell
growth. They change their behaviour when exposed to radiation
and chemicals and mutate, so becoming genes that stimulate
excessive division. This situation is similar to moving car
with the accelerator pressed to the maximum!
|