BIOSC 0160 Lecture Notes - Lecture 11: Hbb, Deoxyribonuclease, Lac Operon

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25 Oct 2017

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Lecture 11: regulation of gene expression (cont. : glucose inhibits beta-galactosidase through positive control. Glucose camp: a molecule that when glucose is high, camp is low. It"s a glucose sensor: crp, binds to camp when glucose is low. Has affinity for upstream of promoter activator binding site: sigma binds to the promoter in prokaryotes. Sigma 70 house keeping sigma and is generally there. Only binds to the promoters that it matches best: the crp and camp complex changes dna sequence and it bends and flexes it, which allows sigma to bind more effectively. This is why the lac operon won"t be expressed when glucose and lactose is present: rna polymerase won"t bind because the promoter is not something the sigma will recognize as well, positive regulation. Eukaryotic gene regulation: control gene expression at levels of transcription, translation, and post-translation.

Related Questions

a. Suppose you isolated a mutation in the CRP gene that results in the production of a CRP protein that cannot bind cAMP. What effect would such a mutation have on expression of the lac operon in the presence versus the absence of lactose (assume that glucose is absent in both cases)?

Answer:

b. Suppose you isolated a different mutation in the CRP gene that results in the production of a CRP protein that binds to the CRP-binding site in the lac promoter even when there is no cAMP available. What effect would this mutation have on expression of the lac operon in the presence versus the absence of lactose, if glucose were also available in both cases?

Answer:

When (glucose, lactose) ___________ levels inside a bacterial cell are low, cyclicAMP levels are (high, low) __________. This is because metabolizes sugars (activate, inhibit) ___________ the enzyme adenylate cyclase, and (activate, inhibit) __________ the enzyme cAMP phosphodiesterase, causing cyclic AMP levels to rise. Consequently, the CAP protein is (Activated, inhibited, unaffected) ___________ by the cyclic AMP and binds to the lac promoter region, and the CAP protein acts like a sigma factor recruiting (DNA, RNA) ___________ polymerase to the promoter. This establishes condition that may lead to the (transcription, replication) __________ of the lac operon if (allolactose, glucose, lactose) _____________ is available to bind to (lac repressor, lacZ, lacY, lacA) _________ protein keeping this protein from binding to the (lacO, lacZ. lacY, lacA) ___________ gene.

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1.In the bacterial lac repressor, which of these occurs:

		A.In the presence of glucose and the absence of lactose, the repressor is actively produced.
		B.The lac operon can be hyper-induced in the presence of low glucose by the 'cAMP binding protein' (CAMP).
		C.In the presence of lactose and the absence of glucose the lac operon is repressed.
		D.Allolactose is a byproduct of Î²-galactosidase, indicating high lactose when it builds up.

2 In eukaryotes the enhancer elements can be quite a distance upstream or downstream from the promoter, and transcriptional regulation is helped by protein:protein interactions.

True

False

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BIOSC 0160 Lecture Notes - Lecture 11: Hbb, Deoxyribonuclease, Lac Operon

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