You are an ecologists working for the CDC trying to determine if a new organic p

Question

You are an ecologists working for the CDC trying to determine if a new organic pesticide is carcinogenic. a. What is the name of the test you should use to determine its mutation rate? b. During the test, his- bacteria were exposed to pesticide for 10 minutes. As a control, another sample of bacteria was not exposed to the pesticide. In both cases, 50 million bacteria were plated on media lacking histidine. Calculate the mutation rate in the presence and absence of the mutagen given the following data. No pesticide: 20 colonies With pesticide: 400 colonies Mutation rate in the presence of the mutagen: 400/50000000 = 8.0 times 10^-6 Mutation rate in the absence of the mutagen: 20/50000000 = 4.0 times 10^-7 c. How much does the mutagen increase the rate of mutation?

Explanation / Answer

I think you need explation of this calculation

The experient is Luria–Delbrück experiment.

Hear mutation rate = number of mutants cell ÷ total number of cells in the culture.

Here the pesticide should have mutated the cells such that it can grow on media lacking in histidine. Only the mutated cells should grow on such a media. Each colony that we get on the plate is a result of a single bacteria. So, no.of colonies indicate the no of mutant cells in the bacteria that we planted.

And so goes the calculation Mutation rate in absence of pesticide= 20(no.of mutated bacterial cells)÷50000000(total no.of bacterial cells planted) = 4.0 × 10-7.

And the same goes for mutation rate in presence of pesticide = 400÷50000000 = 8.0 × 10-6

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