Deck 12: Chromosome Chapter Title Tbd

Question 1

You want to design a repressor protein mutant. Which protein domain is the best target for preventing binding of the corepressor?

A) activator binding site
B) allosteric domain
C) DNA- binding domain
D) helix- turn- helix domain
E) promoter domain

Answer 1

B

Question 2

Disrupting the formation of which stem- loop structure of trpL would decrease the efficiency of transcriptional regulation?

A) 2- 4 (termination) stem loop
B) 2- 3 (antitermination) stem loop
C) 1- 3 (antitermination) stem loop
D) 1- 2 (pause) stem loop
E) 3- 4 (termination) stem loop

Answer 2

E

Question 3

The electrophoresis gel shown below is from a DNase I footprint analysis of an operon transcription control region. Separate samples of control- region DNA were exposed to DNase I and run in the following lanes: uprotected DNA is in lane 1, DNA protected by repressor is in lane 2, and DNA protected by RNA polymerase is in lane 3. Based on the gel, what nucleotide positions are occupied by the repressor and RNA polymerase?

A) 19 through 29 by the repressor and 7 through 24 RNA polymerase
B) 1 through 18 by the repressor and 1 through 6 by RNA polymerase
C) 30 through 35 by the repressor and 7 through 24 by RNA polymerase
D) 1 through 18 by the repressor and 25 through 35 by RNA polymerase
E) 19 through 29 by the repressor and 1 through 6 by RNA polymerase

Answer 3

A

Question 4

Which of the following mutants are noninducible?

A) lacIS
B) lacOC
C) lacI -
D) lacI+
E) lacO+

Question 5

The enzyme fi- galactosidase catalyzes what reaction?

A) lactose -glucose + fructose
B) galactose -glucose + lactose
C) allolactose -glucose + lactose
D) lactose -galactose + glucose
E) glucose -galactose + lactose

Question 6

The presence of which combination of molecules could prevent transcription of a repressible operon?

A) activator + repressor
B) inducer + corepressor
C) repressor + corepressor
D) activator + inducer
E) activator + corepressor

Question 7

In negative control, what molecule would you expect to find bound to the operator if there is no transcription?

A) inducer
B) activator
C) RNA polymerase
D) corepressor
E) repressor

Question 8

Which of these haploid strains produces permease inducibly, but does not produce fi- galactosidase?

A) I - P+ O+ Z - Y+
B) I+ P+ O C Z+ Y+
C) I - P+ O+ Z - Y -
D) I - P+ O+ Z+ Y+
E) I+ P+ O+ Z - Y+

Question 9

During the attenuation of the trp operon, which stem loop leads to polycistronic mRNA synthesis during tryptophan starvation?

A) 1- 2 (pause) stem loop
B) 3- 4 (termination) stem loop
C) 1- 3 (antitermination) stem loop
D) 2- 3 (antitermination) stem loop
E) 2- 4 (termination) stem loop

Question 10

In the lac operon, what acts as the inducer?

A) glucose
B) transacetylase
C) permease
D) allolactose
E) fi- galactosidase

Question 11

Which of the following best describes expression of the lac genes in this partial diploid? I+ P+OC Z- Y+/ I- P+ O+ Z+ Y-

A) fi- galactosidase is made both in the presence and absence of lactose, but permease is only made when lactose is present.
B) Both fi- galactosidase and permease are not made whether lactose is present or not.
C) fi- galactosidase is only made when lactose is present, but permease is made both in the presence and absence of lactose.
D) Both fi- galactosidase and permease are made both in the presence of and in the absence of lactose.
E) Both fi- galactosidase and permease are made only when lactose is present.

Question 12

Which part of the lac operon produces a regulatory protein that is trans- acting?

A) lacO
B) lacI
C) lacZ
D) lacP
E) lacY

Question 13

Which part of the lac operon is cis- dominant?

A) lacI
B) lacY
C) lacA
D) lacZ
E) lacO

Question 14

In a partial diploid of the genotype I- P+ O+ Z- Y+/ I+ P- O+ Z+ Y+, synthesis of

A) fi- galactosidase will be inducible and permease will be constitutive
B) fi- galactosidase and permease will be constitutive
C) fi- galactosidase and permease will be uninducible
D) fi- galactosidase will be uninducible and permease will be inducible
E) fi- galactosidase and permease will be inducible

Question 15

Which of these haploid strains produces fi- galactosidase constitutively but does not produce permease?

A) I+ P+ O- Z+ Y+
B) I- P+ O+ Z+ Y-
C) I - P+ O+ Z+ Y+
D) I+ P+ O+ Z- Y-
E) I- P+ O+ Z- Y+

Question 16

A bacterium is unable to transport lactose into the cell to be broken down. Which gene is likely mutated in this bacterium?

A) lacI
B) lacP
C) lacO
D) lacY
E) lacZ

Question 17

Which region of the lac operon would you target if you want to disrupt the - 10 and - 35 consensus sequences?

A) lacP
B) lacZ
C) lacY
D) lacI
E) lacO

Question 18

In the presence of glucose, where is the lac repressor bound?

A) lacP
B) lacZ
C) lacO
D) lacI
E) The lac repressor is not bound to the operon.

Question 19

Which of the following is FALSE regarding regulation of gene expression in bacteria?

A) Negative control of transcription involves the binding of a repressor protein to a regulatory DNA sequence, with the consequence of preventing transcription.
B) Repressor proteins commonly contain DNA- binding and allosteric domains.
C) There can be transcriptional regulation for the initiation and the amount of transcription, as well as post- transcriptional regulatory mechanisms.
D) Regulated transcription is necessary; constitutive transcription, continuously transcribing genes with no regulatory control, does not occur without mutation.
E) Positive control of transcription involves the binding of an activator protein to a regulatory DNA sequence, with the result of initiating transcription.

Question 20

Which of the following can be mutated to result in constitutive expression from the lac operon?

A) lacO and lacI
B) lacO and lacZ
C) lacI and lacY
D) lacZ and lacI
E) lacZ and lacP

Question 21

Which of the following genotypes and conditions will have the HIGHEST level of trp operon expression?

A) trpL- / tryptophan present
B) trp+ / tryptophan absent
C) trpR- / tryptophan present
D) trp+ / tryptophan present
E) trpP- / tryptophan absent

Question 22

Catabolite repression refers to the repression of the lac operon in the presence of which catabolite?

Question 23

Which of the following is FALSE regarding translational regulation in bacteria?

A) It is the most predominant mode of controlling gene expression in bacteria.
B) Translation repressor proteins regulate translation by binding mRNA near the Shine- Dalgarno sequence.
C) The bacterial insertion sequence (IS10) uses antisense RNA to regulate translation of the mRNA that produces the enzyme transposase.
D) Antisense RNA can bind to a portion of a specific mRNA to which it is complementary.
E) The binding of an mRNA by an antisense RNA can prevent ribosome attachment to the mRNA and block translation.

Question 24

Which enzyme is the product of the lacZ gene?

Question 25

What are the two active sites or "domains" on a repressor protein?

Question 26

Which proteins facilitate RNA polymerase binding at promoters to increase levels of transcription?

Question 27

When both glucose and lactose are available in the growth medium, the presence of which molecule is capable of inducing basal transcription of the lac operon?

Question 28

Which of the following would NOT occur in a phage undergoing induction?

A) The transcription level of the int gene will increase, leading to production of the integrase.
B) Cleavage of the h repressor monomers inactivates the repressor protein.
C) There will be activation of the protease activity of RecA.
D) The transcription level of the xis gene will increase, leading to production of the enzyme excisionase.
E) UV damage to DNA can trigger the switch from lysogeny to the lytic cycle.

Question 29

Binding of which complex increases the ability of RNA polymerase to transcribe the lac
operon?

Question 30

Which of the following regarding riboswitches is correct?

A) They can use repressors to bind to DNA sequences called operators.
B) Low concentrations of a small regulatory molecule can cause cleavage of the mRNA.
C) The binding of small regulatory molecules can generate Shine- Dalgarno sequester stem loops that lead to increased translation.
D) The binding of small regulatory molecules can generate termination stem loops that lead to increased transcription.
E) They can regulate bacterial transcription, translation, and mRNA stability.

Question 31

Which region of the h phage genome enables the linear chromosome to circularize when it enters a host cell?

A) cohesive (cos) site
B) early operators
C) integrase (int) gene
D) IS10
E) excisionase (xis) gene

Question 32

If a corepressor is inhibited, what effect would you expect to see on transcription in a repressible operon?

Question 33

In h phage, which protein, the product of the cI gene, blocks the transcription required to initiate the lytic cycle?

A) repressor
B) cro
C) enhancer
D) integrase
E) operator

Question 34

Which of the following is FALSE regarding how bacteria regulate the transcription of stress response genes?

A) High heat can cause a change in the chaperone proteins.
B) The rpoH gene encodes a sigma factor known as a32 that is active at high temperatures.
C) Holoenzymes containing an alternative sigma subunit are able to recognize the promoters of genes not transcribed by the common bacterial RNA polymerase.
D) Under extreme growth conditions, such as heat stress and starvation, bacteria can induce transcription of alternative sigma factors.
E) Transcription is activated by antitermination, which allows transcription to extend into heat shock genes.

Question 35

Which of the following genotypes and conditions will have the LOWEST level of trp operon expression?

A) trpL- / tryptophan present
B) trp+ / tryptophan absent
C) trpP- / tryptophan absent
D) trpR- / tryptophan present
E) trp+ / tryptophan present

Question 36

What would be the phenotype of an int- h mutant?

A) The cell would build up high levels of h repressor, so lysogeny would be maintained.
B) The phage would be able to enter the lytic cycle, but would not be able to lysogenize.
C) The phage would be able to lysogenize but would not be able to be induced to resume the lytic cycle.
D) The phage would not be able to undergo the lytic cycle, but could lysogenize.
E) Both lytic and lysogenic pathways would be inactivated.

Question 37

Which of the following mutations of the trpL region would be least likely to affect attenuation of trp operon transcription?

A) an insertion of two nucleotides immediately after the polypeptide stop codon
B) an insertion of two nucleotides immediately following the polypeptide start codon
C) a deletion of the uracil nucleotides immediately following region 4
D) a deletion of region 4
E) a deletion of the start (AUG) codon of the trpL polypeptide

Question 38

In the absence of tryptophan, .

A) the repressor binds the corepressor, and operon gene transcription occurs
B) the active repressor binds trpP, so operon gene transcription is repressed
C) the inducer cannot bind trpO, so operon gene transcription occurs
D) the inactive repressor cannot bind trpO, so operon gene transcription occurs
E) the active repressor cannot bind trpO, so operon gene transcription is attenuated

Question 39

Which of the following statements regarding attenuation of the trp operon is NOT true?

A) It is controlled by alternative folding of the mRNA synthesized from the trpL region.
B) If the two tryptophan codons were changed to arginine codons the operon would no longer be sensitive to tryptophan levels but would instead be sensitive to arginine levels.
C) Translation of a trpL coding sequence into a 14- amino acid polypeptide (including the methionine of the start codon and two back- to- back tryptophan codons) is crucial to its function.
D) When tryptophan levels are low, the ribosome will occupy regions 1 and 2 after completing translation of the coding sequence, regions 3 and 4 will pair, and transcription will terminate.
E) When tryptophan levels are high, the formation of a 3- 4 stem loop followed by the poly- U string will prevent expression of the structural genes of the operon.

Question 40

In h phage, a mutation that inactivates which of the following genes should leave the mutated phage strain capable of establishing lysogeny?

A) cro
B) N
C) int
D) cI
E) cII

Question 41

Changing conformation at the active site as a result of binding a substance at a different site is known as .

Question 42

Most of the regulation of gene expression in bacteria occurs at the level.

Question 43

What are the names of the three possible alternative stem loops that can form in mRNA?

Question 44

The genetic switch controlling whether a bacterium enters the lytic or lysogenic cycle relies on the binding of which two proteins?

Question 45

Expression of a(n) alters gene transcription in E. coli by activating transcription of specialized heat stress response genes.

Question 46

What is the role of cis- acting and trans- acting factors in transcription? Explain how these factors play a role in the lac operon, and discuss how complementation can be used to identify where the mutations have occurred (structural genes versus regulatory regions). Which type of mutations can be complemented by a second gene with normal function? Are IS and OC mutants cis- or trans- acting?

Question 47

Northern blot analysis is performed on mRNA isolated from E. coli after growth in a glucose- only medium (lane 1) or a lactose- only medium (lane 2). The blots are hybridized with a probe for a portion of the lacZ sequence. Indicate the expected results for the following bacterial genotypes using dark, light, or no shading to i full, low, or no expression, respectively.
a. I+ P+ O+ Z+ Y+
b. I+ P- O+ Z+ Y+
c. I- P+ O+ Z+ Y+
d. I+ P+ OC Z+ Y+
e. I+ P+ O+ Z+ Y+ and a mutation of the CAP binding site preventing CAP- cAMP binding

Question 48

What is the process by which a bacterium switches from a lysogenic to lytic cycle?

Question 49

In bacteriophage h, if Cro succeeds in binding OR3 within PRM, the cycle is established.

Question 50

What protein cleaves the h repressor monomers to inactivate the repressor protein, and is activated by DNA- damaging agents?

Question 51

In bacteriophage h, if h repressor successfully binds OR1 and OR2 within PR, the _ cycle is established.

Question 52

Antisense control of translation involves the regulation of which enzyme produced by bacterial insertion sequence IS10?

Question 53

In the trp operon, what gene contains the attenuator region?

Question 54

DNA- binding proteins exert control by binding DNA at specific sequences. Describe how DNA and protein interact at the molecular level. Are proteins able to identify specific DNA sequences, or do they bind to all regions with equal frequency? What motifs are commonly found in DNA- binding proteins?

Question 55

What is the purpose of the lac operon, and under what circumstances is it activated? Describe the structure of the lac operon, including the repressor protein, structural genes, and regulatory regions of the operon. What is the role of catabolite repression in the lac operon?

Question 56

Bacteria grown at 45°C initiate expression of which two types of proteins?

Question 57

Using the autoradiograph of a DNA sequencing gel below determine which of the following is the sequence of the 35- bp operon transcription control region.

Question 58

Which molecule functions as the corepressor in the trp operon?

Question 59

In E. coli, the cya gene encodes adenylate cyclase. Will cells that are cya- be able to grow on medium that contains lactose as the sole carbon source? Why or why not?

Question 60

For each of the following E. coli partial diploid strains, indicate whether expression of fi- galactosidase and permease is inducible (I), constitutive (C), or noninducible (N). Assume glucose levels are very low. Which of the strains are able to use lactose as their sole carbon source?

Question 61

What would be the consequences to a h phage that lysogenized in a recA- bacterial cell? Explain why this would occur.

Question 62

Describe the differences between inducible and repressible operons. How does attenuation differ from inducible repressible operons?
Would the lac operon be active if a cell has the following food sources?
a. only lactose
b. only glucose
c. lactose and glucose

Question 63

Suppose a h phage infected a protease- deficient bacterial cell. Would the lytic or lysogenic life cycle be favored? Why?