Question 1

Low concentrations of lactose in a bacterial cell lead to a _______ binding to the operator site of the lac operon and blocking transcription.

Accepted Answer

The answer of Low concentrations of lactose in a bacterial...

Question 2

A bacterial operon is said to be under _______ control if it involves an activator protein that functions to stimulate RNA polymerase to initiate transcription of its genes.

Accepted Answer

The answer of A bacterial operon is said to be...

Question 3

The lac operon is under negative control by a repressor that is sensitive to lactose concentrations and is also under positive control by the activator protein _______, which is sensitive to glucose concentrations.

Accepted Answer

The answer of The lac operon is under negative control...

Question 4

The diagram below illustrates how two _______-acting elements are positioned near the gene that they regulate.

Accepted Answer

The answer of The diagram below illustrates how two _______-acting...

Question 5

DNA is able to form _______, which enable transcription factors at enhancers to interact with the transcription initiation complexes at promoters.

Accepted Answer

The answer of DNA is able to form _______, which...

Question 6

The results from several gene transfer assays carried out to locate regulatory DNA sequences are shown in the table below. Three different transcription factors were used in the assay as probes. Luciferase was used as the reporter protein, and production of light is noted with + signs. No production of light is noted with a 0. The results indicate that _______ of the five DNA sequences tested may be have some sort of gene regulatory role.
 $$\begin{array} { | c | c | c | c | c | c | } 
\hline \begin{array} { c } 
\text { Transcription } \
\text { factor }
\end{array} & \begin{array} { c } 
\text { DNA } \
\text { sequence I }
\end{array} & \begin{array} { c } 
\text { DNA } \
\text { sequence II }
\end{array} & \begin{array} { c } 
\text { DNA } \
\text { sequence III }
\end{array} & \begin{array} { c } 
\text { DNA } \
\text { sequence IV }
\end{array} & \begin{array} { c } 
\text { DNA } \
\text { sequence V }
\end{array} \
\hline \mathrm { X } & + + + & 0 & 0 & 0 & 0 \
\hline \mathrm { Y } & 0 & 0 & + + + & 0 & 0 \
\hline \mathrm { Z } & 0 & 0 & + + + & 0 & + + + \
\hline
\end{array}$$

Accepted Answer

The answer of The results from several gene transfer assays...

Question 7

A researcher has several transcription factors in purified form as well as a DNA fragment in purified form. He suspects the DNA fragment binds to one of the transcription factors. He can use the _______ technique to determine which transcription factor the DNA fragment binds to.

Accepted Answer

The answer of A researcher has several transcription factors in...

Question 8

Chromosomes are organized into multiple loop structures that maintain specificity of enhancers for their cognate genes by the proteins _______ and _______.

Accepted Answer

The answer of Chromosomes are organized into multiple loop structures...

Question 9

Some transcriptional activators have two domains: a _______ domain and an activation domain, each of which carries out specific functions.

Accepted Answer

The answer of Some transcriptional activators have two domains: a...

Question 10

P-TEFb contains a _______ that phosphorylates NELF, DSIF, and serine 2 in the C-terminal domain of RNA polymerase, all of which lead to re-activation of RNA polymerase and transcriptional elongation.

Accepted Answer

The answer of P-TEFb contains a _______ that phosphorylates NELF,...

Question 11

Acetylation of lysine residues on histones causes these proteins to lose _______ charges, which allows the chromatin structure to relax.

Accepted Answer

The answer of Acetylation of lysine residues on histones causes...

Question 12

An investigation identified whether histones nearest specific genes were acetylated or deacetylated. The results are summarized in the table below. Based on these results, it can be predicted that genes _______ would be actively expressed, while the others would not.
 $$\begin{array} { | c | c | c | c | c | c | } 
\hline & \text { Gene A } & \text { Gene B } & \text { Gene C } & \text { Gene D } & \text { Gene E } \
\hline \begin{array} { c } 
\text { Nearest } \
\text { histones }
\end{array} & \text { deacetylated } & \text { acetylated } & \text { deacetylated } & \text { deacetylated } & \text { acetylated } \
\hline
\end{array}$$

Accepted Answer

The answer of An investigation identified whether histones nearest specific...

Question 13

_______ use the energy of ATP hydrolysis to alter and restructure nucleosomes.

Accepted Answer

The answer of _______ use the energy of ATP hydrolysis...

Question 14

Islet cells in the pancreas are the only cells in the human body that produce the hormone insulin. The table below compares the extent of methylation within the promoter region upstream of the gene encoding the insulin protein in three types of human cells. The results provide an example illustrating that methylation of DNA is correlated with transcriptional _______.
 $$\begin{array} { | c | c | } 
\hline \text { Cell type } & \begin{array} { c } 
\text { Extent of methylation of the } \
\text { insulin promoter }
\end{array} \
\hline \text { Pancreatic islet cells } & 0 \
\hline \text { Fibroblasts (skin cells) } & + + + \
\hline \text { Leukocytes (white blood cells) } & + + + \
\hline
\end{array}$$

Accepted Answer

The answer of Islet cells in the pancreas are the...

Question 15

Polycomb proteins are important in repressing gene transcription during development and differentiation. They act by _______ lysine residues in histones.

Accepted Answer

The answer of Polycomb proteins are important in repressing gene...

Question 16

The molecule providing the scaffolding in the figure below to allow multiple chromatin modifications is a(n) _______.

Accepted Answer

The answer of The molecule providing the scaffolding in the...

Question 17

The lac operon is regulated by the binding of an enhancer to sequences just upstream of the promoter.

Accepted Answer

The lac operon is regulated by the binding of a repressor protein to the operator region. The lac repressor protein binds to the operator in the absence of lactose, preventing RNA polymerase from binding to the promoter and transcribing the genes necessary for lactose metabolism. When lactose is present, it binds to the repressor protein, causing a conformational change that releases the repressor from the operator site and allows RNA polymerase to bind and initiate transcription. There is no enhancer involved in this regulation.

Question 18

Some bacterial genes are regulated by transcriptional activators rather than by repressors.

Accepted Answer

This statement is true. Transcriptional activators are proteins that bind to specific DNA sequences and enhance transcription of a gene or genes. This is in contrast to transcriptional repressors which inhibit or decrease transcription of a gene or genes. Some bacterial genes are regulated by one or more transcriptional activators.

Question 19

For each protein-coding gene, there is one promoter and one enhancer that act as regulatory elements for that gene.

Accepted Answer

A gene may have multiple promoters and enhancers that can regulate its expression. Additionally, multiple genes may share the same promoter or enhancer regions.

Question 20

DNA-affinity chromatography is a useful method for purifying individual transcription factors from cell extracts, even though these proteins are present in extremely low quantities.

Accepted Answer

DNA-affinity chromatography takes advantage of the specific binding of transcription factors to DNA sequences, allowing for their purification from cell extracts even when present in low quantities.

Quiz 9: Transcriptional Regulation and Epigenetics