Chapter 17, Problem 6
Predict what would happen to regulation of the lac operon if the lacI gene were moved 50,000 nucleotides upstream of its normal location.
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Activators bind to regulatory sequences in ________ and to ________ polymerase.
A regulon is a set of genes controlled by a. one type of regulator of transcription. b. two or more different alternative sigma proteins. c. many different types of promoters. d. glucose.
Evaluate these statements about regulation of the lac operon. Select True or False for each statement. T/F The lac operon is transcribed at the highest rate when extracellular glucose and lactose are abundant. T/F The repressor protein is bound to DNA of the operator when lactose is present. T/F A mutation in the operator is likely to prevent transcription of the lac operon under any condition. T/F A mutation that alters the catabolite activator protein is predicted to alter the regulation of many different operons.
Explain why it makes sense for the lexA regulatory gene of the SOS regulon to be expressed constitutively.
IPTG is a molecule with a structure much like lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by ββ-galactosidase. Predict what would occur to lac operon regulation if IPTG were added to E. coli growth medium containing no glucose or lactose.
In a mutant that lacks adenylyl cyclase, the enzyme that synthesizes cAMP, predict which of the following conditions of extracellular lactose and glucose would cause regulation of the lac operon to differ from that of wild-type cells. a. no lactose, no glucose b. no lactose, abundant glucose c. abundant lactose, no glucose d. abundant lactose, abundant glucose