Question

Below is a modified version of the Ames test where instead of soaking a filter paper with the test compound, the test compound is layered over the top of the plate. The top left plate was layered with liver extract only. The top right plate was not layered with anything. The bottom right plate was layered with the untreated test compound and the bottom left plate was layered with the test compound after treating it with liver extract.

Control w/ liver extract Control w/o liver extract Test compound w/ liver extract Test compound w/o liver extract

What can you conclude from this test?

That the 'control' and 'test' labels were accidentally switched.

That the liver extract is mutagenic.

That the test compound is made extremely toxic by liver enzymes and the concentration should be lowered in order to have a valid test of mutagenicity.

That the test compound is slightly mutagenic.

Answer 1

Option 4 is correct - the test compound is slightly mutagenic.

Test compound once get exposure to liver extract it's mutagenic property is highly decreased could be because of oxidation by liver enzyme cytochrome P420 oxidase. Hence this compund not able to convert His- mutant Salmonella typhimurium to wild type His+ and thus bacteria does not grown on minimal medium after exposure with liver extract and compound treatment (test comp with liver extract).

Thanks..!