Question 1

Which of the following is an example of negative regulation?&#10;A)A gene is switched on in the presence of an activator.&#10;B)A gene is de-repressed.&#10;C)A gene is induced.&#10;D)A gene is switched off by a repressor protein.

Accepted Answer

Negative regulation refers to the regulation of gene expression by turning off or reducing the expression of a gene product. In this case, a gene is switched off by a repressor protein, which is an example of negative regulation. Choice A, B, and C all refer to positive regulation, which involves the activation or increased expression of a gene product.

Question 2

Transcriptional elements that bind to a DNA molecule where the gene they regulate is located are .&#10;A)trans-acting elements&#10;B)cis-acting elements&#10;C)positive regulators&#10;D)negative regulators

Accepted Answer

cis-acting elements bind to DNA in the same location as the gene they regulate, while trans-acting elements bind to DNA at a different location and interact with cis-acting elements. Positive and negative regulators refer to the effect of the transcriptional element on gene expression, but do not specify the type of regulatory element.

Question 3

Gratuitous inducers .&#10;A)are metabolized like the natural inducer&#10;B)are not broken down&#10;C)are nutrient sources&#10;D)are competitive inhibitors

Accepted Answer

Gratuitous inducers are not broken down by the enzymes they induce, which can lead to overproduction of the target protein.

Question 4

All of the following are associated with two-component regulatory systems except .&#10;A)gratuitous inducer&#10;B)phosphorelay&#10;C)DNA binding regulator&#10;D)sensor kinase

Accepted Answer

Gratuitous inducers are not typically associated with two-component regulatory systems. The other options listed are all components or processes commonly associated with two-component regulatory systems.

Question 5

Which of the following is not an inducer of the lac operon?&#10;A)allo-lactose&#10;B)IPTG&#10;C)glucose&#10;D)lactose

Accepted Answer

Glucose is a repressor of the lac operon, and when present it inhibits the expression of the operon. The other options are all inducers: lactose is the natural inducer, allo-lactose is an isomer of lactose that is produced as a result of lactose breakdown, and IPTG is a synthetic inducer often used in laboratory experiments as a substitute for lactose.

Question 6

Autoregulation occurs when .&#10;A)IPTG binds to LacI&#10;B)allo-lactose binds to LacI&#10;C)a repressor binds to its own gene to prevent transcription&#10;D)CRP binds to cAMP and the the lac operon

Accepted Answer

Autoregulation occurs when a gene product (often a protein) regulates its own production by binding to its own gene's regulatory sequences, thereby influencing the transcription of its own mRNA. This is a form of negative feedback where a repressor protein can bind to the promoter or operator region of its own gene, reducing its own synthesis by preventing transcription.

Question 7

Some nucleotides are involved in transcriptional regulation.

Accepted Answer

Certain nucleotides, such as promoters and enhancers, play a role in regulating transcription by directing the binding of transcription factors and RNA polymerase to specific genes.

Question 8

Alternative sigma factors exist for all of the following except .&#10;A)heat shock&#10;B)nitrogen control&#10;C)flagellar motion&#10;D)exponential phase

Accepted Answer

Alternative sigma factors exist for heat shock (sigma factor 32), nitrogen control (sigma factor 54), and flagellar motion (sigma factor 28), but not specifically for exponential phase.

Question 9

All of the following are examples of transcriptional regulation in prokaryotes except .&#10;A)binding of a repressor to an operator&#10;B)premature termination of RNA polymerase during transcription elongation&#10;C)binding of cAMP-CRP complex to the lac operon of Escherichia coli&#10;D)over-riding termination by anti-terminator proteins

Accepted Answer

Premature termination of RNA polymerase during transcription elongation is an example of post-transcriptional regulation, not transcriptional regulation. The other options all involve regulation at the transcriptional level in prokaryotes.

Question 10

Global regulators .&#10;A)control large numbers of genes in response to a broad,general signals&#10;B)control large numbers of genes in response to a specific signal&#10;C)control small numbers of genes in response to broad,general signals&#10;D)control small numbers of genes in response to a specific signal

Accepted Answer

Global regulators control large numbers of genes in response to broad, general signals, such as environmental changes or stress. Examples include the alternative sigma factor, which switches on a large number of stress-response genes in bacteria, and the transcription factor NF-kB, which is activated in response to a wide variety of inflammatory stimuli in animals.

Deck 16: Regulation of Transcription in Prokaryotes