Question

In the Ames Test, what does the appearance of his+ revertants in the presence of a non-mutagenic control compound indicate?

Answer 1

The appearance of his+ revertants in the Ames Test with a non-mutagenic control indicates spontaneous mutations. These natural genetic reversions allow the bacteria to synthesize histidine without a mutagenic compound, serving as a baseline for comparison with test compounds.

Step-by-step explanation:

In the Ames Test, the appearance of his+ revertants in the presence of a non-mutagenic control compound typically indicates spontaneous mutations. These are the natural genetic reversions that can restore the ability of a histidine auxotrophic strain of Salmonella to synthesize histidine, even without exposure to a potential mutagen.

The number of his+ revertants is compared to the number of revertants that occur when the bacteria are exposed to the test compound. If the number of revertants with the control is similar to that observed with the test compound, this suggests that the test compound is not mutagenic. However, if the test compound produces a significantly higher number of revertants, this could be an indicator of mutagenicity and potential carcinogenicity.

Answer 2

The appearance of his+ revertants in the Ames Test with a non-mutagenic control compound suggests natural spontaneous reversion, not mutagenicity caused by the test compound.

Step-by-step explanation:

In the Ames Test, if his+ revertants appear in the presence of a non-mutagenic control compound, it typically indicates that there is a spontaneous reversion happening in the bacteria. Spontaneous reversions are natural mutations that can occur without the presence of a mutagenic agent.

Therefore, their presence in the Ames Test with a non-mutagenic control means that they are not an indication of the compound being tested as mutagenic. These revertants serve as a comparison for mutations that occur in the presence of potential mutagens.

If the number of his+ revertants is significantly higher with the test compound than with the control, this suggests that the test compound is indeed mutagenic.