Regulation of the lac operon in E. coli (see Chapter 16)...

Question

Regulation of the lac operon in E. coli (see Chapter 16) and regulation of the GAL system in yeast are analogous in that they both serve to adapt cells to growth on different carbon sources. However, the transcriptional changes are accomplished very differently. Consider the conceptual similarities and differences as you address the following.

Compare and contrast the roles of the lac operon inducer in bacteria and Gal3p in eukaryotes in the regulation of their respective systems.

Accepted Answer

Hello, everyone. Let's look at our next question. It says which of the following is not a regulatory gene in yeast. And we look at our four answer choices. We see that there are different Gal genes. Gal, three, gal, four, gal 10 and gal 80. Well, the one here that is not a regulatory gene is choice C gal 10. And that's because we can recall. Gal 10 is one of the structural genes uh in yeast. It, it's one of the genes that codes for proteins that metabolize galactose. So that's along with um gal one, two and seven. Those are the four structural genes for galactose metabolism. So our other three genes here are yeast regulatory genes. Uh So choice A Gal three binds to galactose when galactose is present and that increases its affinity for gal 80 which causes gal 80 to stop inhibiting Gal four, which allows uh transcription to take place when galactose is present. So it uh essentially activates transcription of those structural genes when galactose is present. So that's why it's not our answer since it is a regulatory gene. So we'll cross that out. Choice B gal four, gal four is the, is the regulatory gene that activates transcription. Uh when gal 80 is bound to it, transcription is inhibited. But when galactose is present, as we mentioned previously, gal three binds to galactose that increases its affinity for gal 80 the gal three binds to the gal 80 that releases it from gal four and allows Gala gal four to activate transcription. So it's also regulatory and not our answer. And then finally, Gal 80 as we discussed is regulatory and it's the one that's usually uh bound to GAL four, repressing it when there's no galactose and it's released when gal three has bound to galactose has an increased affinity for GAL A binds to it and it's released from GAL four to allow transcription to take place. So which of the following is not a regulatory gene in yeast twist C gal. See you in the next video.

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