Deck 26: Regulation of Gene Expression

Question 1

All chromatin remodelling complexes are associated with activation of transcription.

Answer 1

False

Question 2

Which of the following BEST describes catabolite repression of the lac operon?

A) The operon is transcriptionally inactive in the absence of lactose.
B) The operon is transcriptionally inactivated by a repressor protein, which binds to glucose.
C) The operon is transcriptionally active when an activator protein binds to the promoter in the absence of glucose.
D) Glucose is the preferred energy source for E. coli.
E) The operon is repressed by its protein products.

Answer 2

C

Question 3

Which of the following BEST describes the SOS response?

A) DNA damage by UV light causes a λ lysogen to be induced to the lytic life cycle.
B) It is an error prone DNA repair system.
C) Activation of RecA by sensing DNA damage and single-stranded DNA.
D) Coordinated activation of a set of unlinked genes whose protein products will collectively help the cell to respond to environmental damage.
E) Transcriptional depression by proteolytic cleavage of the LexA repressor.

Answer 3

D

Question 4

The affinity of the lac repressor for DNA ________ markedly when the inducer binds to the lac repressor.

Question 5

A partial diploid containing a wild type allele for lacI and a lacI mutant that was unable to bind the inducer would:

A) always show low levels of β-galactosidase gene expression.
B) show normal induction in the presence of an inducer.
C) express β-galactosidase at all times.
D) only show normal induction in the presence of an inducer in the absence of glucose.
E) show induction in the presence of an inducer in the presence of glucose.

Question 6

________ mutants of the lac operon express β-galactosidase at high levels in the absence of an inducer, while ________ mutants of the lac operon express only very low levels of β-galactosidase even in the presence of inducer.

Question 7

Which of the following BEST describes transcriptional regulation of the lac operon in E. coli?

A) On in the presence of lactose
B) On in the presence of lactose and presence of glucose
C) Off in the presence of glucose
D) On in the absence of lactose and presence of glucose
E) On in the presence of lactose and absence of glucose

Question 8

Which of the following BEST describes attenuation of the trp operon?

A) The ribosome will stall at adjacent trp codons if tryptophan levels in the cell are low.
B) High levels of tryptophan result in continued translation by the ribosome.
C) A transcription termination sequence forms in the leader mRNA because the ribosome reaches a translation stop codon if tryptophan levels are high.
D) The structural genes are not expressed if tryptophan levels in the cell are high.
E) Regulation of trp operon expression by transcriptional repression by the trp repressor when tryptophan levels in the cell are high.

Question 9

Conformational changes in the cAMP receptor protein upon binding to cAMP trigger ________ of the lac operon in the presence of lactose.

Question 10

The greater complexity of humans compared to worms and flies is due to:

A) a greater number of genes.
B) higher levels of alternative splicing.
C) a much greater number of transcription factors.
D) chromatin structure.
E) combinatorial regulation by a greater number of transcription factors.

Question 11

The λ repressor is inactivated by proteolytic cleavage stimulated by the ________ protein.

Question 12

The physiological inducer of the lac operon is ________.

Question 13

Which of the following is INCORRECT when considering the lac repressor?

A) It is tetramer of two dimers.
B) Binding to the operator site is cooperative.
C) Binding of each dimer is to different regions of the operator.
D) Binding of inducer forces the DNA-binding helices apart so they cannot contact the DNA-binding sites.
E) It is an allosteric protein.

Question 14

A set of linked genes regulated by a common mechanism is called a regulon.

Question 15

The helix-turn-helix is a common protein motif that is able to interact with DNA in the major grooves by both electrostatic and specific interactions between amino acids of the helix and the bases of the DNA.

Question 16

The λ repressor can act as a transcriptional activator as well as a repressor.

Question 17

A partial diploid containing a wild type allele for lacO and a lacO mutant that was unable to bind to the lac repressor would always express β-galactosidase.

Question 18

The trp operon is transcribed when the trp repressor is bound to tryptophan.

Question 19

Catabolite or glucose repression of the lac operon is a regulatory system, which depends on the levels of cAMP in the cell.

Question 20

Nucleosomes very close to the transcription start site in eukaryotes tend to have a high proportion of the histone variants H3.3 and H2A.Z.

Question 21

Epigenetics is the heritable transmission of gene ________ patterns that does not involve a change in the DNA base sequence.

Question 22

Transcriptionally active chromatin usually contains ________ histones, while ________ is normally inhibitory to transcription.

Question 23

ATPase domains of chromatin remodelers associated with transcriptionally active chromatin can contain a bromodomain that interacts specifically with ________ lysines or a chromodomain that interacts specifically with ________ histones.

Question 24

In eukaryotes RNA polymerase is only bound at promoters that are carrying out active transcription.

Question 25

________ are alternative mRNA structures that are produced by binding of a ________ which is often a product of a specific metabolic pathway.

Question 26

________ of specific RNA nucleotides in a process known as RNA editing is a mechanism of altering the protein product encoded by some genes in mammals.

Question 27

DNA methylation in eukaryotes:

A) is part of the epigenetic process.
B) occurs only on cytosine residues.
C) is maintained by specific DNA methyl transferases.
D) is inhibited by 5'-azacytidine.
E) all of the above.

Question 28

Chromatin modifications that tend to inhibit transcription include:

A) methylation at lysine 9 or 27 of histone H3.
B) methylation at lysine 4 of histone H3.
C) ubiquitylation at lysine 119 of histone H3.
D) A, B, and C.
E) A and C.

Question 29

Nucleosome remodeling complexes use ________ to drive changes in chromatin structure.

Question 30

miRNAs are used in gene regulation to:

A) block translation.
B) target mRNA for degradation.
C) cause ribosomes to stall.
D) promote degradation of polyA tails.
E) all of the above.

Question 31

Which of the following is NOT part of initiation of transcription in eukaryotes?

A) Phosphorylation of Ser-5 in the heptad repeats in the C-terminal domain of RNA polymerase II by TF-IIH.
B) Unwinding of the DNA template by TF-IIH
C) Non-specific interactions of general transcription factors at promoters
D) Phosphorylation of Ser-2 in the heptad repeats in the C-terminal domain of RNA polymerase II by P-TEFb.
E) The binding of upstream regulatory proteins

Question 32

RNA interference can be a mechanism of defense against viral infection as well as for regulation of gene expression.