The promoter of an operon is the site to which RNA polymerase binds to begin transcription. Certain base changes in the promoter result in a mutant site that RNA polymerase can’t bind. Would you expect mutations in the promoter that prevents binding of RNA to act in trans on another copy of the operon on a plasmid or only in cis on the copy immediately adjacent to the mutated site?

The promoter of an operon is the site to which RNA polymerase binds to begin transcription. Certain base changes in the promoter result in a mutant site that RNA polymerase can’t bind. Would you expect mutations in the promoter that prevents binding of RNA to act in trans on another copy of the operon on a plasmid or only in cis on the copy immediately adjacent to the mutated site?

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter14: Gene Regulation

Section: Chapter Questions

Problem 2TYU

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A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous transcription of the structural genes (b) no transcription of the structural genes (c) the binding of the repressor to the operator (d) no production of RNA polymerase (e) no difference in the rate of transcription
The lac operon produces enzymes that allow the bacteria E. coli to metabolize lactose, it is in an inducable operon. When lactose is present, will the repressor protein attach or leave the operon? How would this effect the production of lactose producing enzymes?
Which of the following describes the lac operon in E. coli when lactose and glucose is present in the culture medium? Select one: a. CAP inactive and RNA polymerase does not completely bind to the promoter of the lac operon and transcription of lactose-metabolizing enzymes decreases. b. CAP is active and RNA polymerase binds completely to the promoter of the lac operon and transcription of lactose-metabolizing enzymes decreases. c. Catabolite activator protein (CAP) inactive and RNA polymerase does not completely bind to the promoter of the lac operon and transcription of lactose-metabolizing enzymes increases. d. CAP is active and RNA polymerase binds completely to the promoter of the lac operon and transcription of lactose-metabolizing enzymes increases.
In the lac operon, the lacZ gene codes for an enzyme called ____________, which catalyze the breakdown of the sugar __________ into monosaccharides. This enzyme can also hydrolyze the sugar analog ____________, which produces blue pigments following its breakdown. Since the lac operon is not always on the bacterial cells, we add the chemical ________ which prevents the lac depressor from binding to the operators, leading to constitutive expression of the operon.
A mutation occurs in the 5′ UTR of the trp operon that reduces the ability of region 2 to pair with region 3. What will the effect of this mutation be when the tryptophan level is high? When the tryptophan level is low?
Which of the following statements about the trp operon is false? If a mutation in region 2 prevents the formation of the 2 + 3 loop in the 5’UTR transcription levels will increase. The trp operon is an example of negative repressible operon. Formation of the anti-terminator in the 5’UTR of the trp operon occurs when trp levels are low. In the presence of high trp-tRNA, the genes of the trp operon are not expressed. The role of trp is to bind to the repressor protein and activate it.
A mutant strain of E. coli has a premature stop mutation in the lacZgene, resulting in a non-functional b-galactosidase. Otherwise, all other parts of the operon are functional. Which component of an F' plasmid will restore normal regulation and function of the lac operon in the resulting partial diploid?
In most experiments using the lac operon, researchers use the synthetic inducer IPTG to turn on operon expression, instead of lactose or allolactose. What do you think is the advantage of using IPTG?
A lac operon containing one mutation was cloned into a plasmid, which was introduced by transformation into a bacterium containing a wild-type lac operon. The three genes of the chromosomal operon were rendered noninducible in the presence of the plasmid. (a) What kind of mutation in the plasmid operon could have this effect? (b) Suppose the result of transformation was to cause the three plasmid lac genes to be expressed constitutively, at a high level. What type of plasmid gene mutation could have this result?
. In the lac operon of E. coli, if glucose levels increase while lactose levels decrease, what will happen in the regulation of genes controlling the enzymes needed to catabolize lactose? the lac operon will be activated due to cAMP-assisted CAP binding to a site near the promoter the lac operon will be activated due to CAP detachment from a site near the promoter the lac operon will be repressed due to cAMP-assisted CAP binding to a site near the promoter the lac operon will be repressed due to CAP detachment from a site near the promoter all of the above
. What is the role of catabolite activator protein (CAP) in the lactose operon of E. coli? it prevents RNA polymerase from binding to the promoter when lactose levels are high it assists RNA polymerase in binding to the promoter when glucose levels are high it prevents RNA polymerase from binding to the promoter when glucose levels are low it assists RNA polymerase in binding to the promoter when glucose levels are low it prevents RNA polymerase from binding to the promoter when lactose levels are low
What is a specific region in the trp operon that you could mutate so it expresses the trp operon in conditions of excess tryptophan. Why will this mutation cause this? Operon structure: promoter, operater, structural genes promoter - DNA region that is the site of RNA polymerase sigma binding and transcription initiation operator – DNA region that influences gene expression through its interaction with a protein (transcription factor) structural genes – gene whose expression is being regulated; encodes a polypeptide or functional RNA