Question 1

Some corepressors bind to transcription factors at transcription initiation sites and recruit deacetylases that remove acetyl groups from histone lysine groups, leading to condensation of chromatin and repression of transcription.

Accepted Answer

This is a correct statement about how some corepressors function to repress transcription.

Question 2

The light micrograph image below shows a section of a Drosophila chromosome. The arrows indicate regions containing histones that have been deacetylated.

Accepted Answer

The answer of The light micrograph image below shows a...

Question 3

Chromatin remodeling factors are responsible for shuffling and rearranging DNA sequences in chromatin to make them either more or less accessible for transcription.

Accepted Answer

Chromatin remodeling factors do not shuffle or rearrange DNA sequences; they modify the structure of chromatin to regulate the accessibility of DNA for transcription.

Question 4

In eukaryotic cells, genes with methylated DNA tend to be more active than unmethylated genes.

Accepted Answer

In eukaryotic cells, genes with methylated DNA tend to be less active than unmethylated genes. Methylation can lead to the suppression of gene expression.

Question 5

Transmission of information that is not contained within the sequence of DNA to daughter cells at cell division is called epigenetic inheritance.

Accepted Answer

Epigenetic inheritance refers to the transmission of information such as DNA methylation, histone modification or non-coding RNA molecules, which can affect gene expression and cellular phenotype without changes in the DNA sequence, to daughter cells during cell division.

Question 6

lncRNAs assist with changes in chromatin. In embryonic stem cells some of these molecules can act in a repressive role to suppress differentiation and maintain the stem cell state, while others can act in an activating role to allow differentiation to proceed.

Accepted Answer

This statement is true. lncRNAs can play important roles in regulating gene expression and chromatin structure during development, including in embryonic stem cells. Some lncRNAs have been shown to help maintain the stem cell state and prevent differentiation, while others can promote differentiation by promoting changes in chromatin structure and activating certain genes.

Question 7

A mutation in the i gene of the lac operon produces a repressor that retains its DNA binding function but loses its ability to bind to lactose. Will bacteria with this mutant repressor be able to survive in a medium containing lactose as the only carbon source? Explain.

Accepted Answer

The answer of A mutation in the i gene of...

Question 8

Suppose a culture of E. coli is growing in media containing only glucose. The cells eventually deplete this glucose supply. Just as the last bit of glucose is used up, lactose and other sugars become available. How does both the loss of glucose and the addition of lactose affect expression of the lac operon in these cells?

Accepted Answer

The answer of Suppose a culture of E. coli is...

Question 9

The L-arabinose operon in an E. coli strain contains genes that code for enzymes used to break down the sugar L-arabinose. A regulatory gene located upstream from the operon encodes the regulatory protein AraC. AraC undergoes a conformational change when it binds to L-arabinose, and this form of AraC binds to the operator site of the operon, acting as an activator, to stimulate RNA polymerase to begin transcription. Explain whether this is an example of positive or negative control and how this compares to the control mechanism of the lac operon.

Accepted Answer

The answer of The L-arabinose operon in an E. coli...

Question 10

Prokaryotes are single-celled organisms and do not undergo differentiation. Why is it important that these cells have gene regulatory mechanisms, some of which repress transcription and others that stimulate transcription?

Accepted Answer

The answer of Prokaryotes are single-celled organisms and do not...

Question 11

What are three ways in which an enhancer's function differs from that of a promoter?

Accepted Answer

The answer of What are three ways in which an...

Question 12

Describe an electrophoretic mobility shift assay.

Accepted Answer

The answer of Describe an electrophoretic mobility shift assay....

Question 13

If you had genomic DNA and a purified transcription factor, how might you use that to determine the DNA sequence to which the transcription factor binds?

Accepted Answer

The answer of If you had genomic DNA and a...

Question 14

What two different mechanisms do transcription factors use to regulate transcription of eukaryotic genes?

Accepted Answer

The answer of What two different mechanisms do transcription factors...

Question 15

A research lab working with mouse cells characterized three mutant cell lines summarized in the table below. Which of these is most likely to contain a mutated form of P-TEFb? Explain.
 $$\begin{array} { | c | c | c | c | } 
\hline \begin{array} { c } 
\text { Mutant } \
\text { cell line }
\end{array} & \text { Transcription initiation } & \text { Transcription elongation } & \text { Histone modification } \
\hline \mathrm { X } & \text { Functions normally } & \begin{array} { c } 
\text { Unable to make } \
\text { transcripts larger than } 50 \
\text { nucleotides }
\end{array} & \text { Functions normally } \
\hline \mathrm { Y } & \begin{array} { c } 
\text { Lost sensitivity to a } \
\text { transcriptional repressor }
\end{array} & \text { Functions normally } & \text { Functions normally } \
\hline \mathrm { Z } & \text { Functions normally } & \text { Functions normally } & \begin{array} { c } 
\text { Lost ability to } \
\text { deacetylate histones }
\end{array} \
\hline
\end{array}$$

Accepted Answer

The answer of A research lab working with mouse cells...

Question 16

Three amino acids, present in histone tails, that are chemically modified as part of gene regulatory processes are lysine, arginine, and _______.

Accepted Answer

The answer of Three amino acids, present in histone tails,...

Question 17

Refer to the figure below.
  Explain how HDACs function to regulate gene expression.

Accepted Answer

The answer of Refer to the figure below.
  Explain...

Question 18

Methylation of certain lysine residues in histones leads to gene silencing, whereas methylation of other lysine residues in the same histones leads to transcriptional activation. How can methylation lead to these two different outcomes?

Accepted Answer

The answer of Methylation of certain lysine residues in histones...

Question 19

Some chromatin remodeling factors use energy from ATP hydrolysis to slide histones along a chromosome. Explain how this type of activity can regulate gene expression.

Accepted Answer

The answer of Some chromatin remodeling factors use energy from...

Question 20

Long noncoding RNAs (lncRNAs) are often described as having a scaffolding role in the regulation of gene expression. Explain what that means.

Accepted Answer

The answer of Long noncoding RNAs (lncRNAs) are often described...

Quiz 9: Transcriptional Regulation and Epigenetics