Microbio Chpt 14

How do translational riboswitches and transcriptional riboswitches differ? A. Translational riboswitches are mainly observed in Gram-negative bacteria while transcriptional riboswitches are associated with Gram-positive bacteria. B. Translational riboswitches are located in the mRNA trailer while transcriptional riboswitches are in mRNA leader sequence. C. Translational riboswitch effectors bind to ribosomes while transcriptional riboswitch effectors bind to mRNA. D. All of these are differences between translational and transcriptional riboswitches.

Most E. coli antisense RNAs work with a protein called ______ to regulate their target mRNAs. A. CAP B. MicF C. Hfq D. None of the choices are correct.

An sRNA is isolated from a bacterial cell. What would you do to determine whether it is a cis-encoded or a trans-encoded sequence? A. Identify whether or not the sRNA sequence is complementary to the coding strand of mRNA gene target. B. Analyze the molecular position of hydrogen atoms in the sRNA nucleotides. C. Determine whether the sRNA binds to mRNA or to tRNA. D. Find out if the sRNA acts as a transcriptional or as a translational inhibitor.

What is the key factor determining whether or not attenuation will occur when transcription of the E. coli trp operon has been initiated? A. The activity level of adenyl cyclase B. The trp operon repressor C. The level of tryptophan in the environment D. The level of trp-tRNA that is charged with tryptophan

The __________ is a factor-independent termination site found in the leader region of certain operons, which, under the influence of ribosome behavior, controls the continued transcription of that operon. A. modulator B. operator C. attenuator D. terminator

______________ is used to control transcription of some anabolic pathways involved in amino acid biosynthesis. A. Attenuation B. Catabolite repression C. Induction D. All of the choices are correct.

Which is a false statement regarding riboswitches? A. Riboswitches are regions in the 5' untranslated leader of an mRNA. B. The effector molecules that bind to riboswitches are proteins. C. When the effector binds the riboswitch, it may serve to terminate transcription of its target mRNA. D. When the effector binds the riboswitch, it may serve to continue transcription of its target mRNA.

With the E. coli trp operon where both repression and attenuation occur, the extent of regulation achieved by repression is _____________ the extent of regulation achieved by attenuation. A. the same as B. less than C. greater than D. Repression is not used in the regulation of the E. coli trp operon.

The terminator versus anti-terminator function of the T box-based riboswitch used by Gram-positive bacteria to regulate amino acid-related genes is determined by A. the binding of the appropriate uncharged tRNA. B. the rate of leader peptide synthesis. C. the binding of the T box binding protein. D. the utilization of the appropriate sigma factor by RNA polymerase.

In general, riboswitches regulate in Gram-negative bacteria such as Escherichia and in Gram-positive bacteria such as Bacillus. A. transcription; translation B. translation; transcription C. replication; translation D. transcription; replication

In attenuation regulation of the trp operon, which stem loop forms when tryptophan is readily available to the cell? A. 3:4 B. 1:3 C. 2:3 D. 2:4

Which of the following is not a regulatory mechanism used to control the tryptophan operon in Escherichia coli? A. Repression B. Catabolite repression C. Attenuation D. All of the choices are correct.

In terms of transcription regulation, the role of a helix-turn-helix is most similar to that of a(n) . A. zinc finger B. sigma factor C. poly-A tail D. guanine cap

__________ activate repressor proteins, thereby decreasing the synthesis of certain enzymes. A. Inducers B. Corepressors C. Effectors D. Modulators

__________ alter repressor proteins thereby increasing the rate of transcription initiation. A. Inducers B. Corepressors C. Effectors D. Modulators

When a repressor binds to the operator site on the DNA it normally A. inhibits the initiation of transcription. B. reduces the rate of transcription. C. terminates transcription that has already been initiated. D. has no effect on transcription.

Which of the following is not a regulatory mechanism used to control the lactose operon in Escherichia coli? A. Induction B. Catabolite repression C. Attenuation D. All of the choices are correct.

Enzymes that are expressed at a constant level all the time are said to be . A. inducible B. repressible C. constitutive D. attenuated

The site on the DNA to which a repressor protein binds is the __________. A. operon B. operator C. promoter D. regulator

When bound to the DNA, the repressor protein usually prevents attachment of the RNA polymerase to the __________. A. operon B. operator C. promoter D. regulator

Which statement best describes the mechanism(s) of posttranslational regulation of gene expression? A. Allosteric regulation following transcription of mRNA occurs in many biosynthetic pathways. B. Protein synthesis is often repressed by feedback or noncompetitive inhibition. C. Covalent modification of newly synthesized proteins generally has no marked effect on protein function. D. Once a protein is synthesized, there is little to no postranslational modification.

Which of the following statements best explains why microbial geneticists initially focused on regulation of gene expression at the transcriptional, rather than the translational, level? A. By regulating the first step of protein synthesis, cells conserve the greatest amount of energy. B. The process of transcription was best understood by researchers at the time. C. Cellular regulation of transcription is common to all prokaryotic cells. D. The process of synthesizing an mRNA transcript is much less complex than translation of mRNA into protein.

Which of the following is an example of gene regulation at the posttranslational level? A. Alteration of protein structure B. Early termination of an mRNA transcript C. Initiation of protein synthesis D. Prevention of RNA synthesis

When does a cell regulate gene expression? A. Pretranscription through postranslation B. Posttranscription through postranslation C. Pretranscription through pretranslation D. Posttranscription through pretranslation

In two component regulatory systems, the response regulator typically receives a ____________ from the sensor kinase when it has been activated. A. pyruvate group B. phosphoryl group C. acetyl group D. methyl group

While standard two-component regulatory systems typically act to control gene transcription, phosphorelay systems can act either to control gene transcription or to control . A. translation B. protein activity C. DNA replication D. All of the choices are correct.

The sensor kinase for the OmpF: OmpC two-component regulatory system is A. the OmpK protein. B. the EnvZ protein. C. the MicF RNA. D. None of the choices are correct.

The E. coli lac operon has ________ operator sequences. A. one B. two C. three D. four

Which is false regarding the two-component regulatory system in bacteria? A. The system involves a sensor kinase and a response regulator. B. The sensor kinase is phosphorylated by the response regulator when the extracellular environment changes. C. Regulation of OmpF and OmpC porin proteins in E. coli is modulated by this type of system. D. One part of the system is exposed to the external cellular environment while another part is exposed to the cytoplasm.

If Escherichia coli is cultured in broth containing both glucose and lactose, it A. uses glucose preferentially until the supply is exhausted, then uses lactose. B. uses lactose preferentially until the supply is exhausted, then uses glucose. C. uses glucose and lactose simultaneously. D. uses only the glucose (it cannot use lactose as a source of carbon).

What term describes a set of genes that is controlled by a common regulatory protein? A. Codon B. Regulon C. Transcription D. Kinase

In some circumstances, when two different carbon sources are available, growth will occur first using one carbon source, then after a short lag period, growth will resume using the second carbon source. This process is called __________ growth. A. alternating B. bimorphic C. diauxic D. dimorphic

The activity of adenyl cyclase is influenced by A. the phosphotransferase system. B. the presence of lactose in the environment. C. homoserine lactones. D. None of the choices are correct.

The standard or housekeeping sigma factor used most often by E. coli RNA polymerase under normal growth conditions is called sigma ___. A. 70 B. 32 C. S D. E

Acylhomoserine lactones used in quorum sensing regulate their own synthesis by a(n) ____________ system. A. riboswitch B. antisense C. catabolite repression D. autoinduction

During sporulation in Bacillus subtilis, the response regulator that positively controls many genes needed for sporulation and negatively controls genes not needed during sporulation is A. SpoOB. B. SpoOA. C. SpoOF. D. SpoOC.

During sporulation in Bacillus subtilis, inactive precursor forms of new sigma factors are activated at the appropriate time by which mechanism? A. Proteolysis B. Phosphorylation C. RNA-binding D. Chaperone refolding

The sensing of starvation that leads to sporulation in Bacillus subtilis is accomplished by a . A. small RNA B. sensor kinase C. response regulator D. quorum regulatory effector

Cell-to-cell communication by quorum sensing has been shown to be important in the regulation of genes needed for A. virulence. B. biofilm production. C. plasmid transfer. D. All of the choices are correct.

When the Catabolite Activator Protein binds to its binding site in DNA, it A. displaces repressors. B. bends the DNA. C. promotes the assembly of other transcription factors at the promoter. D. eliminates the need for a sigma factor on the part of RNA polymerase.

Guanine tetraphosphate (ppGpp) is particularly associated with which process? A. Spore formation in Bacillus B. Chemiosmosis in Paracoccus C. Stringent response in Escherichia D. Quorum sensing in Vibrio

During the stringent response, ppGpp-regulated genes for amino acid biosynthesis have a(n) _____________ -rich promoter, thus forming a _________________ open initiation complex. A. GC-rich; more stable B. GC-rich; less stable C. AT-rich; more stable D. AT-rich; less stable

Bioluminescence in Vibrio harveyi is due to an alternate sigma factor that prevents _________________________ from binding to Lux mRNA, thus allowing translation of bioluminescent genes. A. antisense B. phosphate C. ribosomes D. autoinducing proteins

Which of the following is not a mechanism of quorum sensing in Vibrio? A. Phosphorelay B. Stringent response C. Autoinduction D. Antisense RNAs

In which situation might methylation of membrane proteins in Escherichia coli initiate a phosphorelay system that evokes clockwise rotation of flagella? A. Presence of a chemorepellent in the extracellular environment. B. Change in environmental osmotic pressure. C. Utilization of lactose due during diauxic growth. D. Cellular population reaches a quorum.

If autophosphorylation of CheA protein does not occur, then Escherichia coli cells must be A. in a gradient of a chemoattractant. B. in a gradient of a chemorepellant. C. tumbling. D. rotating flagella clockwise.

If flagellar rotation of Escherichia coli cells is __________________ , then CheA is ______________________. A. counterclockwise; unphosphorylated B. counterclockwise; autophosphorylated C. clockwise; autophosphorylated D. clockwise; unphosphorylated

Which of the following events occurs initially when Escherichia coli cells are in a gradient of a chemorepellent? A. CheA autophosphorylates B. Flagella rotate clockwise C. Cells tumble D. CheY is phorphorylated

What is the function of cyclic dimeric GMP in bacterial global regulation systems? A. It acts as a secondary nucleotide messenger. B. It is a sensor kinase. C. It converts GTP to cGTP. D. It is an autoinducer.