The field of toxicology uses numerous in vivo
model systems, including the rat, mouse, and rabbit,
to assess potential toxicity and these bioassays
are the mainstay of toxicology testing. However, in
the past several decades, a plethora of in vitro techniques
have been developed to measure toxicity,
many of which measure toxicant-induced DNA damage.
Examples of these assays include the Ames test,
the Syrian hamster embryo cell transformation assay,
micronucleus assays, measurements of sister
chromatid exchange and unscheduled DNA synthesis,
and many others. Fundamental to all of these
methods is the fact that toxicity is often preceded
by, and results in, alterations in gene expression. In
many cases, these changes in gene expression are a