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How is the Ames test used to quantitate mutagenic potential of chemical compounds? Select the TWO best answers.

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The Salmonella tester strain is grown in histidine containing media since it lacks the ability to synthesize its own histidine for protein synthesis; chemical compounds that mimic histidine lead to MORE bacterial growth on the plates.


The Salmonella test strain used in the Ames test contains a mutation in the histidine biosynthetic pathway, which is used to identify compounds that induce back mutations to permit bacterial growth on histidine free plates.


Bruce Ames invented the Ames test to determine which chemical compounds cause human cancer, however bacterial cells are not liver cells and so it is not very useful to prevent gout.


The ratio of bacterial colonies to drug concentration (bc:dc) is used to calculate the mutagenic index of a chemical compound; high bc:dc ratios means the drug functions as a growth factor for the cells.

The Ames test uses filter disks containing chemical compounds to quantitate the level at which the compound is lethal to the Salmonella tester strain; the FEWER colonies on the plate, the more toxic is the chemical regardless of mutagenic potential.

The chemical compound to be tested is added to a filter paper disk and placed on agar plates containing the tester Salmonella strain; potent mutagens result in MORE colonies forming on histidine free plates as compared to control plates.

Histone deficient plates are used to calculate the background mutation rate, which is the control plate for the filter disk experiment. The more colonies growing on the plate, the better the mutagen.