Ames Test Informatic
The Ames test, described by Bruce Ames, is a method that uses bacteria to test whether a given chemical can cause mutation in its DNA - a biological assay to test mutagenic potential of chemicals.
The above schematic describes Ames test in some detail, with a diagram, and is available to download for free, to help you revise. Ames test uses Salmonella Typhimurium bacteria that are auxotrophic (cannot synthesize) histidine and are susceptible to reverse mutations.
A given chemical (a potential mutagen) is mixed with the bacteria before plating them. This chemical can potentially cause either frameshift or point mutations, reversing the gene that causes the auxotrophic trait back to normal. If the chemical ends up being mutagenic (causes mutation), the bacteria will grow on a plate lacking histidine because they have been reverted (a positive Ames test). If the chemical is not mutagenic, the bacteria will not grow in a plate lacking histidine, because they have not been reverted (a negative Ames test).
The Ames test is one way of testing if a chemical causes mutation.