X-gal is a colorless, lactose-like molecule that can be split int...

Question

X-gal is a colorless, lactose-like molecule that can be split into two fragments by ββ-galactosidase. One of these product molecules creates a blue color. The photograph here shows E. coli colonies growing in a medium that contains X-gal. Find three colonies whose cells have functioning copies of ββ-galactosidase. Find three colonies whose cells might have mutations in the lacZ or the lacY genes. Suppose you analyze the protein-coding sequence of the lacZ and lacY genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies?

Accepted Answer

Hello everyone. Let's look at the next question. It says the operator locus of the lack opteron may undergo mutation when it mutates, it precludes the repressor from recognizing and binding to the operator. Which of the following may likely result from this mutation. So we recall that with our lack opera on the lack opteron is induce a ble meaning its usual position is off. It has a repressor sitting there that when lactose is present, it's I summarized along cactus. The aloe lactose binds the repressor that results in the repressor being removed. RNA polymerase can then come in bind to this promoter region and the end result is that the various lack genes will get expressed. So if we have a mutation where this repressor is not able to mind the operator, that means that this state here will occur even without the presence of lactose. So normally you need lactose to formally lactose to remove the oppressor here, there's nothing blocking RNA polymerase from coming in. So we'll see the expression of these genes even without lactose. So let's look at our answer choices. Choice A says black sea black Y and lack A are expressed even in the absence of lactose. And that is correct. Since there's nothing to block RNA polymerase from coming in and transcribing those genes that will just be thorough and look at other choices. Choice B says the regulated genes will not be expressed even in the presence of lactose. Well that's not correct because it is an induce herbal opera on removing the repressor will cause the expression of the genes. Choice C says the genes will produce a different enzyme. Well, that's not correct. You're just removing the repressor, which is blocking RNA polymerase from transcribing those black jeans. You're not changing the genes in any way. And Choice D. The transcription will be stopped. No, the opposite happens, transcription will be initiated because RNA polymerase can now bind with the repressor. Missing. See you in the next video.

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