Please find the attached file. 3. In the Ames test, a presumed mutagen is plated with a tester strain of bacteria whichcannot synthesize the amino acid histidine due to a single base pair change in one geneof the histidine biosynthetic pathway. For example, in one tester strain, the gene forimidazole glycerolphosphate dehydratase, which catalyzes step 6 in the biosyntheticpathway, will have a TGG codon (tryptophan) changed to TGA codon (stop). This testerstrain makes a truncated enzyme which cannot catalyze step 6. If this single adenine inthis codon is mutated to a guanine in one of the bacteria, then that cell of the testerstrain can now make the enzyme and be able to grow on the histidine-minus medium.mutation events will this tester strain be able to detect?TGAWhat mutational events would another tester strain with a AAA codon (lysine)changed to a TAA (stop) codon in the same gene be used to detect?Renair

Answered: 3. In the Ames test, a presumed mutagen…

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Please find the attached file.

3. In the Ames test, a presumed mutagen is plated with a tester strain of bacteria which
cannot synthesize the amino acid histidine due to a single base pair change in one gene
of the histidine biosynthetic pathway. For example, in one tester strain, the gene for
imidazole glycerolphosphate dehydratase, which catalyzes step 6 in the biosynthetic
pathway, will have a TGG codon (tryptophan) changed to TGA codon (stop). This tester
strain makes a truncated enzyme which cannot catalyze step 6. If this single adenine in
this codon is mutated to a guanine in one of the bacteria, then that cell of the tester
strain can now make the enzyme and be able to grow on the histidine-minus medium.
mutation events will this tester strain be able to detect?
TGA
What mutational events would another tester strain with a AAA codon (lysine)
changed to a TAA (stop) codon in the same gene be used to detect?
Renair

Expert Solution

Step 1

Ames test is used to test for a mutation causing the ability of a chemical in the DNA (deoxyribonucleic acid) in the test organism by using bacteria. A positive test indicates that the chemical is mutagenic and can potentially act as a carcinogen. It uses strains of Salmonella Typhimurium having genes carrying a mutation in histidine synthesizing genes. The strains grow when histidine is provided in the medium, hence they are auxotrophic mutant. The chemical is then tested with the tested strain whether it can cause mutation and restrore the mutation which would allow the bacterial strain to grow in the histidine minus medium. The result is compared to the control strain which has normal back mutations.

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