Exam 2

Question 1

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.

Answer 1

C) glucose is low and lactose is present.

Question 2

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

Answer 2

D) cAMP ; switches on

Question 3

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.

Answer 3

A) active and can bind to the operator.

Question 4

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

Answer 4

A) True

Question 5

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

Answer 5

A) True

Question 6

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

Answer 6

A) True

Question 7

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.

Answer 7

E) inactive and cannot bind to the operator.

Question 8

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

Answer 8

E) trp repressor.

Question 9

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

Answer 9

B) False

Question 10

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

Answer 10

A) True

Question 11

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.

Answer 11

D) conjugation.

Question 12

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.

Answer 12

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

Question 13

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.

Answer 13

A) normal regulation of lactose metabolism.

Question 14

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.

Answer 14

B) constitutive expression of lac Z+.

Question 15

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.

Answer 15

B) constitutive expression of lac Z+.

Question 16

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.

Answer 16

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

Question 17

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.

Answer 17

D) The lac genes would never be expressed efficiently.

Question 18

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.

Answer 18

D) The lac genes would never be expressed efficiently.

Question 19

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.

Answer 19

C) The lac genes would be expressed continuously.

Question 20

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.

Answer 20

D) The lac genes would never be expressed efficiently.

Question 21

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.

Answer 21

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

Question 22

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.

Answer 22

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

Question 23

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

Answer 23

B) naked DNA in solution

Question 24

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

Answer 24

A) only the transformed cells will grow

Question 25

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

Answer 25

A) True

Question 26

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

Answer 26

A) True

Question 27

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

Answer 27

A) competent

Question 28

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.

Answer 28

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

Question 29

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.

Answer 29

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

Question 30

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

Answer 30

A) phage DNA integrated into host cell genome

Question 31

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

Answer 31

c) in all Catabolite-Sensitive Operons

Question 32

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

Answer 32

a) Regulatory cascade

Question 33

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

Answer 33

e) A and B

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

``` 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 ```

Answer 40

Α.  galactosidase, which splits x-gal

Question 41

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

Answer 41

B. False

Question 42

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

Answer 42

B. False

Question 43

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

Answer 43

C. a and b

Question 44

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

Answer 44

A. True

Question 45

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

Answer 45

False

Question 46

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

Answer 46

B) False

Question 47

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

Answer 47

A) True

Question 48

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

Answer 48

A) True

Question 49

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

Answer 49

A) True