Describe the purpose of the Ames test. How are his⁻ bacteria used in the Ames test? What mutational event is identified using his⁻ bacteria?

Key Concepts

Ames Test Purpose

The Ames test is a widely used assay that evaluates the mutagenic potential of chemical compounds. It assesses whether a substance can cause mutations in the DNA of a test organism, typically a strain of bacteria. By identifying mutagens, the Ames test helps in assessing the potential carcinogenic risk of chemicals to humans.

his⁻ Bacteria

His⁻ bacteria are mutant strains of bacteria that lack the ability to synthesize histidine, an essential amino acid. In the Ames test, these bacteria are exposed to the test substance, and if mutations occur that restore their ability to produce histidine, it indicates that the substance is mutagenic. This restoration is a key indicator of genetic change due to the test compound.

Mutational Events

The mutational event identified using his⁻ bacteria in the Ames test is the reversion mutation, where a mutation in the bacterial DNA restores the original function lost in the his⁻ strain. This event signifies that the test substance has induced a genetic change, allowing the bacteria to regain the ability to synthesize histidine, thus providing evidence of mutagenicity.