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Unformatted text preview: Microbial Genetics - BIOL 518 Exam #4 - Fall 2009 Name: Multiple choice. Choose ALL of the correct answers for each question. There may be more than one correct answer per question. (48 points total). 1: At a class I catabolite activator protein (CAP) dependent promoter, CAP A: Interacts with the carboxyl end of the alpha subunit (alpha-CTD) in RNAP B: Stimulates the open complex C: Is bound by glucose D: Strengthens the binding of RNAP to the promoter (closed complex) 2: Negative regulation of the araBAD operon: A: involves the formation of a DNA loop that may block RNA polymerase binding to the promter. B: occurs in the presence of arabinose, since there is no need to biosynthesize arabinose if it is availble. C: occurs by the CRP-cAMP complex binding to DNA upstream of araI1 . D: involves the two DNA binding domains of a single AraC protein dimer binding to the araI1 and araO2 sites, respectively. 3: According to the light switch model for how the AraC protein responds to the absence or presence of arabinose: A: In the presence of arabinose, the AraC protein is constrained such that it can not bind to adjacent DNA sites and prefers to form a DNA loop. B: In the absence of arabinose, the very amino terminal residues of AraC contact the C-terminal domain of AraC. C: In the presence of arabinose, the very amino terminal residues of AraC bind over the arabinose binding pocket, making interactions with the arabinose. D: AraC only becomes phosphorylated in the presence of arabinose, and therefore only activates transcription under these conditions. 4: In Bordetella pertussis , the pertussis toxin A: has transcription of its encoding gene activated by a phosphorylated response regulator termed BvgA B: is encoded on a lysogenic bacteriophage C: is typically expressed after the bacteria adheres to the surface of the epithelial cells D: is controlled by the auto-phosphorylation levels of the BvgS sensor kinase 5: Activation of the cholera toxin encoding operon ( ctxAB ) in Vibrio cholera : A: only occurs when the organism finds itself in the small intestine of a host (such as a human). B: requires that ToxS and TcpH stabilize the dimer forms of ToxR and TcpP, respectively. C: requires that ToxR and TcpP together directly activate transcription of the toxT operon. D: requires that ToxT directly activates transcription of the ctxAB operon. 6: Expression of the glutamine synthetase gene (glnA) A: is regulated by the activity of a uridylyltransferase termed GlnD B: is upregulated when glutamine binds to GlnD and removes UMP from a protein called PII C: PII with UMP bound, dephosphorylates NtrB D: is upregulated by low levels of glutamine 7: In the presence of both arabinose and glucose, A: araBAD expression would be fully on....
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