Question

I am a student conducting a test with the Ames Assay. This assay uses a strain of bacteria that has a mutation in an amino acid synthesizing operon, which doesn't allow it to synthesize its protein. The idea of the assay states that if an exposed chemical has mutagenic properties, the bacteria will revert back to the wild type.

If I have a test chemical, what are the odds that, if the chemical is actually mutagenic, the bacteria will actually revert back to the wild type, instead of having something else be mutated? Aren't there so many other base pairs of DNA to be mutated, that the odds of the mutation be reversed are little to none? Is there something about the specific gene that makes that area more prone to a mutation?

Answer 1

The odds of bacteria reverting back to the wild type in the Ames assay depend on the specific mutation and the mutagenic properties of the chemical being tested. The particular mutation in the amino acid synthesizing operon is essential for the bacteria's survival, so if the chemical causes a reverse mutation, the bacteria will revert back to the wild type.

Step-by-step explanation:

The odds of the bacteria reverting back to the wild type in the Ames assay depend on the specific mutation and the mutagenic properties of the chemical being tested. While it is true that there are many other base pairs of DNA that can be mutated, the particular mutation in the amino acid synthesizing operon is significant because it causes the bacteria to be unable to synthesize its own protein. This mutation is essential for the bacteria's survival, so if the chemical being tested is mutagenic and causes a reverse mutation in this operon, the bacteria will be able to synthesize its protein again and revert back to the wild type.