Do we know what causes colorectal cancer? We don't know the
exact cause of most colorectal cancers, but a great deal of
research is being done in this area. Researchers are beginning
to understand how certain changes in DNA can cause normal cells
to become cancerous. DNA is the chemical in each of our cells
that makes up our genes -- the instructions for how our cells
function. We usually look like our parents because they are the
source of our DNA. But DNA affects more than just how we look.
Some genes contain instructions for controlling when our cells
grow, divide, and die. Certain genes that speed up cell division
or help cells to live longer are called oncogenes. Others that
slow down cell division, or cause cells to die at the right
time, are called tumor suppressor genes. Cancers can be caused
by DNA mutations (defects) that turn on oncogenes or turn off
tumor suppressor genes. Mutations in several different genes
seem to be needed to cause colorectal cancer. Some DNA mutations
may be passed from gener