Following the spill of a mixture of chemicals into a small pond, bacteria from the pond are tested and show an unusually high rate of mutation. A number of mutant cultures are grown from mutant colonies and treated with known mutagens to study the rate of reversion. Most of the mutant cultures show a significantly higher reversion rate when exposed to base analogs such as proflavin and 2-aminopurine. What does this suggest about the nature of the chemicals in the spill?

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Hi, everyone. Here's our next problem. It says cyanobacteria were found to have been experiencing a high rate of mutation due to chemical pollution caused by an oil spill. Researchers perform muto genesis assays using various known mutagens. The results show that the highest rate of aversion occurs when the bacteria are exposed to U V radiation. Which of the following statements is therefore true about the impact of the oil spill on cyanobacteria. Choice A the spill is muto GIC due to excessive nutrients. Choice B the spill is more mugen for cyanobacteria. Only choice C the spill will most likely make the cyanobacteria go extinct or choice D the spill can cause damage similar to that of U V radiation. So we have a situation where cyanobacteria have been exposed to chemicals on an oil spill and are experiencing a high rate of mutation. Well, we can go ahead and eliminate, then choice C the spill will most likely make the cyanobacteria go extinct. They're not dying off, they're mutating. So we're going to go ahead and cross that one out and we have choice. A, the spill is immunogenic due to excessive nutrients. Well, this isn't a fertilizer spill, maybe for a fertilizer spill, we might look at that but these are chemicals in an oil spill. So that's pretty unlikely to be causing any sort of mutation. Excessive nutrients would usually cause um excessive growth and perhaps problems from overgrowth of cyanobacteria in their environment, not genetic mutation. So we'll cross out choice a pretty easily there. So finally, we have B the spill is more muto GIC for cyanobacteria only or D it can cause damage similar to U V radiation. Well, again, choice B pretty easy to eliminate because there's no comparison here. We're not comparing what's happening with cyanobacteria versus other things. So that isn't going to be something that our assay is going to tell us about. Well, we've just got choice D left and this is correct. But let's talk through. So we understand why it's the correct answer other than just by process of elimination, that's fine on a test time is of the essence. But we want understanding here. So usually in a Muto Genesis essay, you're testing potential muto genes to see if they cause mutation. In this case, we already have mutation. So we're testing mutated cyanobacteria and it says we tested them or tested with known munos. So we're not looking at whether those things mutate are known to mutate, whether those substances we're testing will mutate things or not. We know they will cause mutations. We're trying to say something about the mutations that happened already. Well, when you do mute agenesis essay like this, you're looking to see when your mutagen will cause the mutant bacteria that you're testing to revert to wild type. So, we've started with mutated cyanobacteria. We've, we're testing with known Mutis that we're treating them with and we're looking for bacteria that are reverted too wild type. And our problem tells us that the highest rate of aversion. So highest cases when the bacteria reverted to all type was with U V radiation. So what does this tell us if U V radiation is most likely to reverse the mutations caused by the oil spill? Then we can say choice D the spill can cause damage similar to that of U V radiation. So that is why choice D is the correct answer here. See you in the next video.

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Key Concepts

Mutagenesis and Mutation Types

Base Analogs as Mutagens

Reversion Rate and Mutation Analysis