The Ames test is a screening test that is used to help identify
chemicals that affect the structure of DNA. The test exposes
Salmonella bacteria to chemicals and looks for changes in the
way bacteria grow. These changes result from mutations that
occur when the structure of DNA is altered in certain places.
Many chemicals that cause mutations can cause cancer in animals
or in people. When the test was developed, it was thought that
most of the chemicals that produce results in the Ames test
could also cause cancer. It was hoped that this simple test
would be an easy way to find cancer-causing chemicals. Over
time, the test was found to be a less reliable predictor of
carcino-genesis than had been hoped. Some chemicals that are
known to cause cancer do not test positive in the Ames test and
some chemicals that test positive do not cause cancer.
Nonetheless, the test is still considered an important part of
assessing the safety of new chemicals. The Ames test uses
strains of Salmonella that have been altered to