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PMG > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

The lac operon is expressed when
A) glucose is high and lactose is present.
B) glucose is high and lactose is absent.
C) glucose is low and lactose is present.
D) glucose is low and lactose is absent.
E) glucose is low, regardless of the presence or absence of lactose.

A

C) glucose is low and lactose is present.

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2
Q 
When in a complex with \_\_\_\_\_\_\_\_, the CAP protein binds to the CAP site and \_\_\_\_\_\_\_\_ the expression of the lac operon.
		A)	glucose ; switches on
		B)	glucose ; switches off
		C)	lactose ; switches on
		D)	cAMP ; switches on
		E)	cAMP ; switches off
A

D) cAMP ; switches on

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3
Q

In the absence of lactose, the lac repressor is
A) active and can bind to the operator.
B) active and cannot bind to the operator.
C) inactive and cannot bind to the promoter.
D) inactive and can bind to the operator.
E) inactive and cannot bind to the operator.

A

A) active and can bind to the operator.

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4
Q

The inducer of the lac operon is an isomer of lactose.
A) True
B) False

A

A) True

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5
Q

When RNA polymerase is bound to the lac promoter sequence, transcription of the lac operon is on.
A) True
B) False

A

A) True

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6
Q 
The trp operon consists of \_\_\_\_\_\_\_\_ structural genes.
		A)	one
		B)	two
		C)	three
		D)	four
		E)	five
A

A) True

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7
Q

In the absence of tryptophan, the trp repressor is
A) active and can bind to the operator.
B) active and cannot bind to the operator.
C) inactive and cannot bind to the promoter.
D) inactive and can bind to the operator.
E) inactive and cannot bind to the operator.

A

E) inactive and cannot bind to the operator.

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8
Q 
In the presence of tryptophan, tryptophan binds to the
		A)	operator.
		B)	promoter.
		C)	RNA polymerase.
		D)	trp genes.
		E)	trp repressor.
A

E) trp repressor.

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9
Q

In the presence of tryptophan, transcription of the trp operon is on.
A) True
B) False

A

B) False

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10
Q

An operon is a group of genes that is under the control of a single operator site.
A) True
B) False

A

A) True

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11
Q 
Cells of anE. colistrain that aretrplac Zmetbiowere mixed with cells of anE. colistrain that aretrplac Zmetbioand cultured for several hours. Then cells were removed, washed, and transferred to minimal media containing lactose as the only sugar source. A few cells were able to grow on minimal media with lactose, and formed colonies. How did these few cells becometrplac Zmetbio?
A)  transformation.  
B)  transduction.  
C)  sexduction.  
D)  conjugation.  
E)  transposition.
A

D) conjugation.

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12
Q

How many lac Z genes were present in the cells described in the previous problem (11) that were able to grow on minimal media?
A) Only 1, the lac Z- allele on the bacterial chromosome.
B) Only 1, the lac Z+ allele on the bacterial chromosome.
C) Two, the lac Z- allele on the bacterial chromosome and the lac Z+ allele on the bacterial chromosome.
D) Two, the lac Z- allele on the bacterial chromosome and the lac Z+ allele on the F’ episome.
E) Only 1, the lac Z+ allele on the F’ episome.

A

D) Two, the lac Z- allele on the bacterial chromosome and the lac Z+ allele on the F’ episome.

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13
Q

How would you describe the regulation of lactose metabolism in the cells described in problem 11 that were able to grow on minimal media with lactose as a nutrient?
A) normal regulation of lactose metabolism.
B) constitutive expression of lac Z+.
C) inability to synthesize the lac Z+ gene product, ß-galactosidase.
D) lac Z+ gene is inducible, but unable to be repressed by high glucose.
E) no synthesis of the lac I gene product, the lac repressor.

A

A) normal regulation of lactose metabolism.

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14
Q

An E. coli strain that is lac Z is conjugated with E. coli cells carrying an F’ plasmid with the plac Oc lac Z DNA sequence on the episome. The Oc is a mutation of the lactose operator that is no longer able to bind the lac I gene product which codes for the lac repressor. How would the expression of the lac Z be regulated in the resulting cells that are diploid for the lactose regulatory region and the lac Z gene?
A) normal regulation of lactose metabolism.
B) constitutive expression of lac Z+.
C) inability to synthesize the lac Z+ gene product, ß-galactosidase.
D) lac Z+ gene is inducible, but unable to be repressed by high glucose.
E) no synthesis of the lac I gene product, the lac repressor.

A

B) constitutive expression of lac Z+.

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15
Q

Predict the phenotype of a lacI mutant.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

B) constitutive expression of lac Z+.

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16
Q

If a second wild type or normal copy of the lacI gene (just lacI and not lacZ, lacY, or lacA) is introduced into the lacI mutant cell, what would be the phenotype of this partial diploid (also referred to as a merodiploid)?
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

B) The lac genes would be expressed efficiently only in the presence of lactose.

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17
Q

Predict the phenotype of a lacI S or “super-repressor” mutant. A lacI S mutant synthesizes a repressor that cannot bind to the inducer.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

D) The lac genes would never be expressed efficiently.

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18
Q

Predict how a lacI S mutant would be affected by the construction of a merodiploid that has a second normal copy of the lacI gene.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

D) The lac genes would never be expressed efficiently.

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19
Q

Predict the phenotype of an operator mutant (Oc) which would prevent the binding of the repressor.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

C) The lac genes would be expressed continuously.

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20
Q

Predict the phenotype of a promoter mutant (lacP) which has a mutation in the promoter for the lac operon.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently only in the presence of lactose.
C) The lac genes would be expressed continuously.
D) The lac genes would never be expressed efficiently.

A

D) The lac genes would never be expressed efficiently.

21
Q

Predict the phenotype of a lacZ mutant, which has a mutation in the gene for β-galactosidase.
A) The production of all protein products would be affected.
B) The production of β-galactosidase would be affected, but other protein products would be unaffected.
C) The production of β-galactosidase would be affected, and the production of some other protein products might also be affected.
D) The production of β-galactosidase would be unaffected, but other protein products would be affected.

A

B) The production of β-galactosidase would be affected, but other protein products would be unaffected.

22
Q

Predict the phenotype of a lacY mutant, which has a mutation in the gene for lactose permease.
A) The lac genes would be expressed efficiently only in the absence of lactose.
B) The lac genes would be expressed efficiently until the lactose supply in the cell is exhausted.
C) The lac genes would be expressed continuously.
D) Expression of the lac genes would cease immediately.

A

B) The lac genes would be expressed efficiently until the lactose supply in the cell is exhausted.

23
Q 
DNA transformation involves the transfer of DNA via 
 A) pili 
 B) naked DNA in solution 
 C) a restriction endonuclease 
 D) a bacteriophage
A

B) naked DNA in solution

24
Q

When DNA from an ampicillin resistant organism is brought into an ampicillin sensitive organism by transformation and the product is grown on agar containing ampicillin
A) only the transformed cells will grow
B) only donor cells will grow
C) all cells grow
D) no cells grow
E) only ampicillin sensitive cells grow

A

A) only the transformed cells will grow

25
Q

In transformation, both strands of donor DNA enter the recipient cell.
A) True
B) False

A

A) True

26
Q

Donor DNA is combined with recipient DNA by homologous recombination.
A) True
B) False

A

A) True

27
Q

A bacterial cell that is able to take up naked DNA is said to be
A) competent
B) liable
C) infected

A

A) competent

28
Q

Which of these describes a similarity between the lac and ara operons?
A) Expression of structural genes does not occur at high glucose concentrations.
B) lacI and araI both encode trans acting factors.
C) Binding of a regulatory protein is prevented in the presence of an inducer.
D) All of these are similarities.
E) None of these are similarities.

A

A) Expression of structural genes does not occur at high glucose concentrations.

29
Q

Attenuation of the trp operon:
A) Occurs when transcription is complete before translation begins.
B) Is mediated by the trp repressor protein.
C) Occurs in the presence of high levels of tryptophan.
D) All of the above.
E) None of the above.

A

C) Occurs in the presence of high levels of tryptophan.

30
Q

A prophage is
A) phage DNA integrated into host cell genome
B) phage DNA being actively expressed
C) phage protein left outside the bacterium
D) toxic to the host bacterial cell

A

A) phage DNA integrated into host cell genome

31
Q

CAP contains an “activating region” that has been proposed to participate in direct protein-protein interactions with RNA polymerase and/or other basal transcription factors.

a) in the Lac operon
b) in the Trp operon
c) in all Catabolite-Sensitive Operons
d) in Ara operon
e) in Lac and Ara operons

A

c) in all Catabolite-Sensitive Operons

32
Q

Transcriptional Regulation during the development of a typical large DNA phage the ________________ products are responsible for regulation the transcription (turn on or off the transcription of other genes)

a) Regulatory cascade
b) Regulatory genes
c) Lytic regulation

A

a) Regulatory cascade

33
Q

In specialized transduction

a) requires a phage that uses the lysogenic cycle for reproduction
b) only certain bacterial genes can be transferred and these genes, as you will see, must exist on either side of the prophage
c) a phage that uses the lytic cycle for reproduction
d) Whatever piece of bacterial DNA happens to get packaged within the phage is the genetic material that will be transferred between cells.
e) A and B

A

e) A and B

34
Q

When the defective phage enters a new bacterial cell
A) only phage DNA integrates into the chromosome of the new host cell
B) only bacterial DNA from the previous bacterial host integrates into the chromosome of the new host cell
C) both phage DNA and bacterial DNA integrate into the chromosome of the new cell host
D) the DNA is destroyed

A

C) both phage DNA and bacterial DNA integrate into the chromosome of the new cell host

35
Q

In the process of specialized transduction
A. all the genes of the first bacterial host are transferred to the second bacterial host by a phage
B. only a few specific genes from one bacterial cell are transferred to the second bacterial host by a phage
C. only a few specific genes from the bacteriophage are transferred to the second bacterial host by a phage
D. the phage lyses the recipient bacterium

A

B. only a few specific genes from one bacterial cell are transferred to the second bacterial host by a phage

36
Q

In specialized transduction
A) any random bacterial gene can be transduced
B) only genes on a plasmid can be transduced
C) only phage genes near the site of the recipient bacteria integration site can be transduced
D) only bacterial genes near the site of integration of the phage DNA can be transduced

A

D) only bacterial genes near the site of integration of the phage DNA can be transduced

37
Q

Plasmids can best be described as:
A. small, circular DNA molecules that can exist independently of chromosomes commonly found in bacteria
B. a complex membrane structure that covers the chromosome of bacteria
another name for a chloroplast

A

A. small, circular DNA molecules that can exist independently of chromosomes commonly found in bacteria

38
Q

In insertional inactivation
A. if foreign DNA is inserted, the beta galactosidase marker is inactivated, and the colonies remain white
B. if foreign DNA is inserted, the beta galactosidase marker is inactivated, and the colonies turn blue
C. if foreign DNA is inserted, the beta galactosidase marker is activated, and the colonies remain white
D. if foreign DNA is inserted, the beta galactosidase marker is activated, and the colonies turn blue

A

A. if foreign DNA is inserted, the beta galactosidase marker is inactivated, and the colonies remain white

39
Q

If host cells are ampicillin sensitive and are plated on a medium containing ampicillin
A. only cells that have not taken up the ampicillin resistant vector can grow
B. only cells that have taken up the ampicillin resistant vector can grow
C. all cells will grow
D. ampicillin is inactivated

A

B. only cells that have taken up the ampicillin resistant vector can grow

40
Q 
The lac z gene marker codes for
Α.	 galactosidase, which splits x-gal
Β.	 galactosidase, which makes x-gal resistant to splitting
C.	ampicillin resistance
white colonies
A

Α.  galactosidase, which splits x-gal

41
Q

When foreign DNA and plasmid are both cut with the same restriction enzyme and mixed together, all molecules will form recombinants.
A. True
B. False

A

B. False

42
Q

When beta galactosidase cleaves x-gal, white colonies result.
A. True
B. False

A

B. False

43
Q 
Theta replication is 
A.	unidirectional
B.	bidirectional
C.	a and b
D.	Start at the oriC
A

C. a and b

44
Q

ColE1 plasmid do not require a plasmid-encode protein to initiate replication at their oriV, only an RNA primer synthesized from the plasmid
A. True
False

A

A. True

45
Q

The iteron plasmids only use host proteins in the replication
A. True
False

A

False

46
Q

The plasmids members of the same incompatibility group are able to coexist
A) True
B) False

A

B) False

47
Q

Curing a plasmid is when bacteria lose the plasmid during the cell division
A) True
B) False

A

A) True

48
Q

In the rolling circle replication, the plasmid has single strand origin and double strand origin regions
A) True
B) False

A

A) True

49
Q

Most of the plasmids require a plasmid-encoded protein called Rep
A) True
B) False

A

A) True

PMG (3 decks)

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