Identify the purpose of and outline the procedure for the Ames test.

Identify the purpose of and outline the procedure for the Ames test.

purpose: access chemicals for their ability to cause mutations
1. two cultures are prepared of salmonella bacteria that have lost the ability to synthesize histidine (histidine-dependent)

2. the suspected mutagen is added to the experimental sample only; rate liver extract (an activator) is added to both samples

3. each sample is poured onto a plate of medium lacking histidine. the plates are then incubated at 37 degrees Celcius for two days. only bacteria whose histidine-dependent phenotype has mutated back (reverted) to histidine-synthesizing will grow into colonies

4. the number of colonies on the experimental and control plates are compared. the control plate may show a few spontaneous histidine-synthesizing revertants. the test plates will show an increase in the number of histidine-synthesizing revertants if the test chemical is indeed a mutagen and potential carcinogen. the higher the concentration of mutagen used, the more revertant colonies will result