Question

1. You just found a new compound “ABC” to be carcinogenic via the Ames test using His^-Salmonella. Which of the experimental plates listed below will have the most colonies?
   1. His^-Salmonella, rat liver enzymes
   2. His^-Salmonella, rat liver enzymes, compound “ABC”
   3. His^-Salmonella, compound “ABC”

What test can you do to confirm that “ABC is carcinogenic?

Answer 1

Ames test is a mutagenicity test.

• The test is used to estimate the mutagenic potentiality (possible carcinogenicity) of substances or to determine a chemical or a sample is a mutagen.
• Bacterial strain used for Ames test is Salmonella typhimurium.
• The strain has mutant gene, due to which the strain is unable to synthesize amino acid histidine (His-).
• The concept of Ames test is based on back mutation, which converts His- to His+.
• Thus, the revertant bacteria are able to grow on media lacking histidine.
• Hence, stronger is the mutagen, the higher probability will be its mutagenic or carcinogenic capability.
• About 90% of mutagen detected in Ames test may act as carcinogenic in animals.
• Liver enzymes like S9 helps in activating the proantigens, which may not give the corrects result without activation.

Thus, maximum back mutation will result with the carcinogen and liver extract with His- Salmonella.

Answer: b