In an experiment employing the methods of the Ames test, two stra...

Question

In an experiment employing the methods of the Ames test, two strains of Salmonella are used. Strain A contains a base-substitution mutation, and Strain B contains a frameshift mutation. Four plates are prepared to test the mutagenicity of the compound ethyl methanesulfonate (EMS). Plate 1 is a control plate with Strain A and S9 extract but no EMS. Plate 2 is also a control plate and contains Strain B and S9 extract but no EMS. Plate 3 contains Strain A along with S9 extract and EMS, and Plate 4 contains Strain B, S9 extract, and EMS.

Why is the S9 extract added to each of the plates?

Accepted Answer

Hi, everyone. Let's look at our next question. In a mutagen assay. S nine extract is added to salmonella plates to activate proc carcinogens and mutagens. Which of the following best explains why. This step is important in the essay. Choice. A proc carcinogens and mutagens are inert and cannot cause mutations unless they are activated by metabolic enzymes. Choice B salmonella bacteria are incapable of metabolizing proc carcinogens and mutagens without the help of sine extract. Choice C the S nine extract produces a, provides a source of nutrients that enhances the growth of salmonella bacteria which in turn increases their mugen. And choice DS nine extract is a type of antibiotic that selectively kills salmonella bacteria that have mutations. Well, as we think about this question, we first off can just eliminate right away. Choice of D we don't want to kill off salmonella bacteria that have mutations. We want to see when mutations occur. The whole point of this essay is to test the mugen of certain compounds. So let's think about what this S nine extract is that has to be added. And S nine extract is a sample of liver enzymes and that is precisely because many proc carcinogens and mutagens, uh don't actually cause problems until they're metabolized in the body. And that would occur in the liver. So this sort of mimics the metabolic activity of the body because again, we're testing this in salmonella, but we're interested in what the problem is it gonna cause for people. So we need to add these liver enzymes to mimic that, processing that those chemicals will receive in the body, which mostly occurs through the liver. So that would be choice. A proc carcinogens and mutagens are inert and cannot cause mutations unless they are activated by metabolic enzymes. Just looking at our other answer. Choices. Choice of B says salmonella, bacteria are incapable of metabolizing proc carcinogens and mutagens without the help of S nine extract. Um Well, this is not quite correct. They do need the S nine extract, but that's to mimic the activity of the liver. Salmonella obviously doesn't have livers. They would process these things in their own way. But that isn't similar enough to the metabolic activity of a more complex organism. So that's why choice B is not correct. And then finally, to AC says the S nine extract provides a source of nutrients, but that's not a correct description. Again, that S nine extract is composed of liver enzymes to mimic that meta metabolic activity in the body. So that's why that's not our answer. So again, the step of adding S nine extract, why is that important in a mugen the assay choice. A proc carcinogens and muto genes are inert and cannot cause mutations unless they're activated by metabolic enzymes. See you in the next video.

Key Concepts

Ames Test

S9 Extract

Types of Mutations

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