1. At Thanksgiving dinner, your great aunt refuses to eat with plastic silverware and proudly exclaims that she has discarded all plastics because âthey cause cancer.â You wonder if chemicals you commonly use are mutagenic. You recall your time in BY 331, Genetics, and realize that you can use the Ames test to test for reversion of a point mutation in the HisG gene in the bacteria S. typhimurium. You added the chemical you wish to test into the growth medium for the bacteria. You carefully plated an equal number of cells on each mutagenesis plate. You also calculated percent survival for chemical treated cells relative to untreated cells. Remember that the plate media for survival is not selective. A summary of the results is shown below.
Chemical
Percent Survival
Number of Revertants (# of His+ colonies/selective plate)
No chemical added
100
28
Chemical A
50
1400
Chemical B
70
20
Chemical C
100
7
A. What medium must be used in the selective plate as part of the Ames test? Explain how a mutation gives rise to a revertant in this experiment.
[Type your answer here, use as much space as necessary to completely answer the question]
B. You are initially surprised to see revertants in the absence of any chemical that you are testing, but you realize that this is normal. Explain a specific way in which a revertant can arise in the absence of an added mutagen.
[Type your answer here, use as much space as necessary to completely answer the question]
C. Which chemicals would you identify as containing a mutagen? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
D. Which chemicals would you identify as possibly antimutagenic? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
1. At Thanksgiving dinner, your great aunt refuses to eat with plastic silverware and proudly exclaims that she has discarded all plastics because âthey cause cancer.â You wonder if chemicals you commonly use are mutagenic. You recall your time in BY 331, Genetics, and realize that you can use the Ames test to test for reversion of a point mutation in the HisG gene in the bacteria S. typhimurium. You added the chemical you wish to test into the growth medium for the bacteria. You carefully plated an equal number of cells on each mutagenesis plate. You also calculated percent survival for chemical treated cells relative to untreated cells. Remember that the plate media for survival is not selective. A summary of the results is shown below.
| Chemical | Percent Survival | Number of Revertants (# of His+ colonies/selective plate) |
| No chemical added | 100 | 28 |
| Chemical A | 50 | 1400 |
| Chemical B | 70 | 20 |
| Chemical C | 100 | 7 |
A. What medium must be used in the selective plate as part of the Ames test? Explain how a mutation gives rise to a revertant in this experiment.
[Type your answer here, use as much space as necessary to completely answer the question]
B. You are initially surprised to see revertants in the absence of any chemical that you are testing, but you realize that this is normal. Explain a specific way in which a revertant can arise in the absence of an added mutagen.
[Type your answer here, use as much space as necessary to completely answer the question]
C. Which chemicals would you identify as containing a mutagen? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
D. Which chemicals would you identify as possibly antimutagenic? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
