UNCW BIO 335 test 3 material

The maltose operon contains three genes: malE, malF and malG. Transcription of this operon would result in _____ mRNA transcript(s) which encodes _____ stop codon(s).

A) 1; 1

B) 3; 1

C) 3; 3

D) 1; 3

D) 1; 3

A gene is inducible and under negative control. Which of the following pairs will allow expression of this gene?

A) Activator + repressor

B) Activator + corepressor

C) Repressor + inducer

D) Repressor + corepressor

C) Repressor + inducer

Which of the following is TRUE of an operon that is only regulated by positive control?

A) An operator sequence in the DNA would follow the promoter

B) The promoter is likely a poor match to the consensus sequence for binding of the sigma factor

C) A corepressor would be required to bind the activator protein

D) The activator protein would not require a small molecule effector

B) The promoter is likely a poor match to the consensus sequence for binding of the sigma factor

Consider the trp operon in E. coli. What would be the result if the U-rich sequence after region 4 was replaced with a G-rich sequence?

A) Attenuation would occur when tryptophan levels are adequate

B) Attenuation would occur when tryptophan levels are low

C) Attenuation would not occur when tryptophan levels are adequate

D) Attenuation would occur when tryptophan levels are excessive

C) Attenuation would not occur when tryptophan levels are adequate

A mutation in the lacI gene prevents the LacI protein from binding allolactose. What will the expression level of the operon be in the presence of lactose?

A) No transcription or a basal (i.e. very low) level of transcription

B) The operon would be turned on by a corepressor instead of an inducer

C) The operon would always be turned on (i.e. highly expressed)

D) Transcription will only occur when glucose is present

A) No transcription or a basal (i.e. very low) level of transcription

Consider regulation of the lac operon in E. coli. Which of the following is TRUE of the cell in the presence of high levels of glucose and lactose?

A) Adenylyl cyclase is not active

B) The repressor protein is not bound to the operator

C) The operon is transcribed at high levels

D) A and B

E) A, B and C

D) A and B

Which of the following is an example of post translational regulation in bacteria?

A) Binding of a translational repressor to the ribosomal binding site B) Phosphorylation of an enzyme

C) Binding of an antisense RNA to an mRNA transcript

D) Altering the structure of the mRNA transcript by binding of a small molecule

B) Phosphorylation of an enzyme

How are eukaryotic transcription factors regulated?

A) Covalent modification

B) Binding of an effector molecule

C) Protein-protein interactions

D) A and B E) A, B and C

E) A, B and C

What general transcription factor is most often affected by regulatory transcription factors in eukaryotes?

A) TFIIB

B) TFIID

C) TFIIE

D) TFIIF

B) TFIID

A particular gene has a mutation in its NFR that causes it to bind abnormally tightly to histones. What effect would you expect this mutation has on the expression of this gene?

A) The expression of the gene would be abnormally high

B) The effect on gene expression is impossible to predict

C) The gene would encode a different protein instead

D) The expression of the gene would be abnormally low

E) The promoter of the gene will be constantly available to general transcription factors and RNA polymerase

D) The expression of the gene would be abnormally low

Two genes in a bacterial cell may be expressed at different levels, but each individual gene is expressed at the same level under all environmental conditions.

a) True

b) False

b) False

Which of the following interact with DNA in a non-sequence specific manner?

a) Histones

b) Sigma factor

c) A and B

a) Histones

DNA binding proteins involved in the regulation of gene expression bind irreversibly to specific DNA sequences.

a) True

b) False

b) False

Which of the following bonds would mediate the interaction between a regulatory DNA binding protein and the double-stranded DNA?

a) Non-covalent bonds

b) Covalent bonds

c) A and B

a) Non-covalent bonds

Which of the following is TRUE of alternative sigma factors in E. coli

a) Alternative sigma factors bind to promoters with a different -35 sequence element than the main sigma factor (sigma 70).

b) Alternative sigma factors regulate the expression of genes under specific environmental conditions or stresses.

c) Alternative sigma factors are always abundant in the cell and bind to the sigma 70 promoter with high affinity.

d) A and B

e) B and C

d) A and B

Which of the following sequences does a bacterial repressor bind to?

a) Promoter

b) Operator

c) Activator

d) Terminator

b) Operator

Genes controlled by an activator protein typically have a promoter sequence that has a weak affinity for binding sigma factor.

a) True

b) False

a) True

In bacteria, small effector molecules control whether or not repressors and activators bind to DNA.

a) True

b) False

a) True

When considering gene regulation in bacteria which of the following is TRUE of inducible genes?

a) An inducer will bind to a repressor putting it in a conformation that can bind to the operator

b) Inducible genes are typically involved in catabolic pathways

c) Inducible genes are only under negative control

d) A and B

e) A, B and C

b) Inducible genes are typically involved in catabolic pathways

If a bacterial gene is regulated by both positive and negative control which of the following sites would you find in the DNA?

a) Operator site

b) Activator site

c) Effector site

d) A and B

e) A, B and C

d) A and B

The lac operon consists of three genes: lacZ, lacY and lacA. How many promoters are required to express these three genes?

a) There is no promoter in front of these genes as they are co-transcribed with lacI

b) 1

c) 2

d) 3

b) 1

Which of the following is TRUE of the lac operon when lactose is present?

a) Lactose is converted to allolactose by beta-galactosidase

b) Allolactose binds to the repressor protein

c) The repressor protein is in a conformation that binds to the operator

d) A and B

e) A, B and C

d) A and B

Which of the following is TRUE of positive control when considering the regulation of the lac operon?

a) Adenylyl cyclase is inhibited by glucose

b) If cAMP levels are high the CAP protein will bind to the CAP site in the DNA

c) CAP protein binding to the CAP site in the DNA stabilizes the RNA polymerase at the promoter

d) A and B

e) A, B and C

e) A, B and C

Consider the regulation of the lac operon in E. coli. Which of the following is TRUE when the cell is in the presence of both glucose and lactose?

a) The repressor is not bound to the operator in the DNA

b) CAP is not bound to the CAP site in the DNA

c) There is a high level of transcription of lacZYA

d) A and B

e) A, B and C

d) A and B

The trp operon is a repressible operon regulated by both negative and positive control.

a) True

b) False

b) False

Which of the following is TRUE when there is an excessive amount of tryptophan present in the cell?

a) Charged tRNATrp serves as the corepressor and binds to the repressor protein

b) Free Tryptophan serves as the corepressor and binds to the repressor protein

c) The repressor is bound to the corepressor, putting it in a conformation that does NOT bind to the operator

d) A and C

e) B and C

b) Free Tryptophan serves as the corepressor and binds to the repressor protein

What is the purpose of the attenuation mechanism for regulating the trp operon?

a) To sense the presence of all uncharged tRNAs in the cell

b) To sense the amount of free tryptophan in the cell

c) To sense the amount of tRNAs charged with tryptophan in the cell

d) To sense the amount of repressor protein available for negative regulation of the operon

c) To sense the amount of tRNAs charged with tryptophan in the cell

Which of the following is involved in the attenuation mechanism in the regulation of the trp operon?

a) A leader region in the mRNA containing codons for Tryptophan

b) An intrinsic termination signal

c) coupled transcription-translation

d) A and B

e) A, B and C

e) A, B and C

Consider the regulation of the trp operon. Which of the following is TRUE when there is no tryptophan present and coupled transcription-translation is occurring?

a) The repressor is not bound to the operator

b) The ribosome stalls at the Trp-Trp codons in the mRNA molecule

c) An intrinsic termination signal forms in the mRNA

d) A and B

e) A, B and C

d) A and B

Which of the following is a mechanism for modulating the activity of eukaryotic transcription factors?

a) Binding of small molecule effectors

b) Formation of homodimers

c) Covalent modification

d) All of the above

d) All of the above

Consider the regulation of the lac operon in E. coli. Which of the following is TRUE when the cell is in the presence of both glucose and lactose?

a) The repressor is not bound to the operator in the DNA

b) CAP is not bound to the CAP site in the DNA

c) There is a high level of transcription of lacZYA

d) A and B

e) A and C

d) A and B

The attenuation mechanism for regulating the trp operon depends on the structure of the leader region of the mRNA transcript and coupled transcription-translation.

a) True

b) False

a) True

Which of the following is TRUE of DNA methylation in eukaryotes?

a) DNA methylation occurs at CpG sequences

b) Methylation typically inhibits transcription

c) de novo methylation is a highly regulated process

d) A and B

e) A, B and C

e) A, B and C

Which of the following is TRUE of epigenetic changes in gene expression?

a) Epigenetic changes can be heritable, meaning these changes can be passed to daughter cells following cell division.

b) Epigenetic changes may involve changes in chromatin structure

c) Epigenetic changes result in a change in the DNA sequence

d) A and B

e) A, B and C

d) A and B