Answer the following questions about the Ames test for mutagenicity. The Ames te
ID: 164619 • Letter: A
Question
Answer the following questions about the Ames test for mutagenicity. The Ames tester strain is designated Salmonella enterica His. What does this mean? (ii) The Ames tester strain has been constructed to use an error prone DNA repair pathway. Why? (iii) The Ames tester strain has a short (an R LPS), in its outer membrane. Why? (iv) When a chemical give a positive Ames test the number of colonics on glucose-salts medium is significantly higher than on the control plate (solvent only, no compound). Why?Explanation / Answer
1. The Salmonella strain carry mutation in histidine synthesis genes. They are autotrophic mutants and can grow only in the presence of histidine, that’s the reason they are designated as Salmonella enteric His.
2. This is to make the test more sensitive.
3. These strains have mutations that produce a deficient lipopolysaccharide.
4. The carcinogenic substances produce mutations in the strain and make it a prototroph, thus making it grow on medium containing glucose salts. It will not grow on the control as the strain initially are autotrophic mutants which require initially some nutrients to grow and later due to the mutations caused by carcinogen they become prototroph and grow independently without any need of nutrients in the medium.