Question 1

________ __________is the enzyme needed to bring lactose into the bacterial cell.

Accepted Answer

Galactoside permease

Question 2

Which of the following would be effective in blocking transcription from the lac operon in the presence of permease?

Accepted Answer

An antibody to RNA polymerase would block transcription by preventing the enzyme from initiating the transcription process.

Question 3

Which of the following bond creates the linkage between glucose and galactose?

Accepted Answer

The bond that links glucose and galactose is a glycosidic bond, specifically a β-1,4-glycosidic bond, which is a type of covalent bond. This bond can indeed be broken down by the enzyme β-galactosidase, making all the given choices correct.

Question 4

Which of the following techniques is most useful in determining if RNA polymerase has initiated transcription from the lac DNA template?

Accepted Answer

The run-off transcription assay is the most useful technique in determining if RNA polymerase has initiated transcription from the lac DNA template. This technique involves halting transcription at a specific point, isolating the RNA transcript, and analyzing it to see if it corresponds to the expected product. Southern analysis and DNA fingerprinting are both DNA-based techniques and do not directly measure transcription. DNA sequencing and RACE can provide information about the DNA template sequence and transcribed RNA sequence, but do not necessarily indicate if transcription has initiated.

Question 5

Which of the following is most likely to occur if the level of glucose is low in a bacterial cell?

Accepted Answer

When glucose levels are low in a bacterial cell, cyclic AMP (cAMP) levels increase. This cAMP binds to the catabolite activator protein (CAP), also known as CRP (cAMP receptor protein), enabling it to assist in stimulating transcription of the lac operon by facilitating the binding of RNA polymerase to the promoter.

Question 6

The ara operon is controlled by the _____________ protein.

Accepted Answer

The answer of The ara operon is controlled by the...

Question 7

Which of the following organisms would produce functional lac products in the presence of IPTG?

Accepted Answer

The "+" indicates a functional lac product. Therefore, only the organisms with a "+" for both the S1 and S2 sites will produce functional lac products in the presence of IPTG. Therefore, option C (I⁺ O⁺ Z⁺ Y⁺ A⁺) is the correct answer.

Question 8

$\beta$-galactosidase cleaves the disaccharide lactose into __________ and ____________.

Accepted Answer

The answer of $\beta$-galactosidase cleaves the disaccharide lactose into __________...

Question 9

The identity of the following molecule is

Accepted Answer

The answer of The identity of the following molecule is
...

Question 10

Which of the following is true about the regulation of the trp operon?

Accepted Answer

All of the choices are true about the regulation of the trp operon. An aporepressor (the inactive form of a repressor) is involved in controlling the trp operon. Tryptophan, the product of the operon, acts as a corepressor, binding to the aporepressor and activating it to bind to the operator region and inhibit transcription. Attenuation, a mechanism that regulates transcription by premature termination of mRNA synthesis, also plays a role in controlling the trp operon. Finally, the regulation of the trp operon involves negative control, where a repressor protein binds to the operator and prevents transcription.

Question 11

Which of the following statements is true about a lac operon with this genotype? I^-d O⁺ Z⁺ Y^- A^-

Accepted Answer

The genotype of this lac operon includes the absence of the lac repressor (IS) and the presence of constitutively active promoters (P1 and P0) and an operator site with a mutation that prevents binding of the lac repressor (OS). Additionally, there is a mutation in the structural gene for β-galactosidase (YS) that makes it insensitive to negative regulation by the lac repressor. These mutations together result in a lac operon that is constitutively expressed and is nonrepressible.

Question 12

Which of the following is true about the action of CAP at the lac promoter?

Accepted Answer

CAP-cAMP complex binding to the lac activator-binding site facilitates the recruitment of RNA polymerase to the promoter, enhancing transcription of the lac operon.

Question 13

In the presence of glucose the lac operon is kept inactive by _________ _________.

Accepted Answer

The answer of In the presence of glucose the lac...

Question 14

________ is a term used to describe a mechanism in which a protein controls it's own regulation.

Accepted Answer

The answer of ________ is a term used to describe...

Question 15

If an operon is under negative control it means that the operon is never operational.

Accepted Answer

Negative control means that a repressor protein is bound to the operator region, preventing transcription. When a specific inducer binds to the repressor protein, it undergoes a conformational change that releases it from the operator, allowing transcription to proceed. Therefore, the operon is only operational when the repressor protein is inhibited by the inducer.

Question 16

Regions of the 5'-UTRs of mRNAs that alter their structures to control gene expression are called _____________________.

Accepted Answer

The answer of Regions of the 5'-UTRs of mRNAs that...

Question 17

Identify the allosteric protein.

Accepted Answer

Repressors are allosteric proteins that can change their conformation upon binding to an effector molecule, which affects their ability to bind to DNA and regulate gene expression.

Question 18

In an in vitro transcription assay to detect the level of transcription from a lac operon,one of the RNA precursors was tagged with a fluorescent label on the $\beta$-phosphate.Which of the following is a likely outcome if transcription occurred?

Accepted Answer

The answer of In an in vitro transcription assay to...

Question 19

Which of the following is absent in an operon?

Accepted Answer

Introns are not present in operons. Operons are found in prokaryotic organisms, which typically do not have introns in their DNA. Operons consist of an operator, promoter, and one or more structural genes that are transcribed together to produce a polycistronic mRNA.

Question 20

In the process of creating a trp operon mutant,the region for the riboswitch was accidentally deleted.Which of the following would be a likely observation in the transcription assays?

Accepted Answer

The riboswitch region is involved in the attenuation mechanism, which controls the expression of the trp operon by regulating premature termination. Without the riboswitch, attenuation would be impaired and the operon would be constitutively expressed. RNA polymerase can still bind to the promoter in the absence of the riboswitch, and termination would not be triggered. The chance of an aptamer binding to the mRNA 5'UTR is not affected by the deletion of the riboswitch region.

Quiz 7: Operons: Fine Control of Bacterial Transcription

__is the enzyme needed to bring lactose into the bacterial cell.

Which of the following would be effective in blocking transcription from the lac operon in the presence of permease?

Which of the following bond creates the linkage between glucose and galactose?

Which of the following techniques is most useful in determining if RNA polymerase has initiated transcription from the lac DNA template?

Which of the following is most likely to occur if the level of glucose is low in a bacterial cell?

The ara operon is controlled by the _____________ protein.

Which of the following organisms would produce functional lac products in the presence of IPTG?

$\beta$ -galactosidase cleaves the disaccharide lactose into and __.

The identity of the following molecule is

Which of the following is true about the regulation of the trp operon?

Which of the following statements is true about a lac operon with this genotype? I^-d O⁺ Z⁺ Y^- A^-

Which of the following is true about the action of CAP at the lac promoter?

In the presence of glucose the lac operon is kept inactive by _ _.

________ is a term used to describe a mechanism in which a protein controls it's own regulation.

If an operon is under negative control it means that the operon is never operational.

Regions of the 5'-UTRs of mRNAs that alter their structures to control gene expression are called _____________________.

Identify the allosteric protein.

In an in vitro transcription assay to detect the level of transcription from a lac operon,one of the RNA precursors was tagged with a fluorescent label on the $\beta$ -phosphate.Which of the following is a likely outcome if transcription occurred?

Which of the following is absent in an operon?

In the process of creating a trp operon mutant,the region for the riboswitch was accidentally deleted.Which of the following would be a likely observation in the transcription assays?

Quiz 7: Operons: Fine Control of Bacterial Transcription

________ __________is the enzyme needed to bring lactose into the bacterial cell.

Which of the following would be effective in blocking transcription from the lac operon in the presence of permease?

Which of the following bond creates the linkage between glucose and galactose?

Which of the following techniques is most useful in determining if RNA polymerase has initiated transcription from the lac DNA template?

Which of the following is most likely to occur if the level of glucose is low in a bacterial cell?

The ara operon is controlled by the _____________ protein.

Which of the following organisms would produce functional lac products in the presence of IPTG?

β\betaβ -galactosidase cleaves the disaccharide lactose into __________ and ____________.

The identity of the following molecule is

Which of the following is true about the regulation of the trp operon?

Which of the following statements is true about a lac operon with this genotype? I-d O+ Z+ Y- A-

Which of the following is true about the action of CAP at the lac promoter?

In the presence of glucose the lac operon is kept inactive by _________ _________.

________ is a term used to describe a mechanism in which a protein controls it's own regulation.

If an operon is under negative control it means that the operon is never operational.

Regions of the 5'-UTRs of mRNAs that alter their structures to control gene expression are called _____________________.

Identify the allosteric protein.

In an in vitro transcription assay to detect the level of transcription from a lac operon,one of the RNA precursors was tagged with a fluorescent label on the β\betaβ -phosphate.Which of the following is a likely outcome if transcription occurred?

Which of the following is absent in an operon?

In the process of creating a trp operon mutant,the region for the riboswitch was accidentally deleted.Which of the following would be a likely observation in the transcription assays?

__is the enzyme needed to bring lactose into the bacterial cell.

$\beta$ -galactosidase cleaves the disaccharide lactose into and __.

Which of the following statements is true about a lac operon with this genotype? I^-d O⁺ Z⁺ Y^- A^-

In the presence of glucose the lac operon is kept inactive by _ _.

In an in vitro transcription assay to detect the level of transcription from a lac operon,one of the RNA precursors was tagged with a fluorescent label on the $\beta$ -phosphate.Which of the following is a likely outcome if transcription occurred?