Question 1

In a type I topoisomerase, the active site amino acid _________ is covalently bound to the free _______ end of the cut in the DNA.

Accepted Answer

A)  serine; 3'
B)  serine; 5'
C)  tyrosine; 3'
D)  tyrosine; 5'
E)  none of the aboveF) C) and D)
G) B) and C)

Question 2

Which of the subunits of DNA polymerase III is responsible for the high processivity of the enzyme?

Accepted Answer

A)   β\betaβ 
B)   γ\gammaγ 
C)   δ\deltaδ 
D)   δ\deltaδ '
E)   ε\varepsilonεF) A) and C)
G) C) and D) A

Question 3

A mutation in a gene results in a mutant phenotype. What occurs if the wild-type phenotype is restored by a mutation at another site in the gene?

Accepted Answer

A)  reversion
B)  silent mutation
C)  conjugation
D)  silent conjugation
E)  suppressionF) C) and D)
G) B) and E)

Question 4

What enzyme that is part of the primosome is responsible for unwinding of the DNA ahead of the replication fork?

Accepted Answer

A)  topoisomerase
B)  helicase
C)  primase
D)  clamp loading complex
E)  single-stranded binding proteinF) B) and C)
G) A) and C)

Question 5

If a segment of a eukaryotic chromosome contained three origins of replication (at the sites indicated with arrows), how would the segment appear when replication was about half completed?

Accepted Answer

The answer of If a segment of a eukaryotic chromosome...

Question 6

Replication of DNA in E. coli occurs in what type of fashion?

Accepted Answer

A)  unidirectional
B)  bidirectional
C)  multidirectional
D)  directionality can change depending upon specific conditions in the cell
E)  none of the aboveF) D) and E)
G) B) and C)

Question 7

Which of the following was evidence that DNA polymerase I was not responsible for the bulk of DNA synthesis in vivo?

Accepted Answer

A)  the requirement for an RNA primer
B)  the presence of both polymerase and exonuclease activity in the same enzyme
C)  the number of enzyme copies in each cell far exceeded the number of replication forks
D)  the requirement for Mg2+
E)  none of the aboveF) C) and D)
G) B) and D)

Question 8

For the following sequence, indicate the RNA primer that would be needed to start synthesis of the Okazaki fragment.
5'-A-A-C-T-A-G-A-C-C-A-G-A-3'

Accepted Answer

3'-U-U-G-A...

Question 9

What protein complexes with ATP and cardiolipin to initiate E. coli DNA replication by creating negative superhelical tension in the double stranded DNA?

Accepted Answer

A)  DnaA
B)  DnaB
C)  DnaC
D)  DnaJ
E)  DnaKF) C) and E)
G) A) and D)

Question 10

Which of the following describes the correct sequence of enzyme activity upon the lagging strand?

Accepted Answer

A)  primase, DNA ligase, DNA polymerase I, DNA polymerase III
B)  primase, DNA polymerase I, DNA polymerase III, DNA ligase
C)  DNA polymerase III, primase, DNA polymerase I, DNA ligase
D)  primase, DNA ligase, DNA polymerase III, DNA polymerase I
E)  primase, DNA polymerase III, DNA polymerase I, DNA ligaseF) A) and B)
G) None of the above

Question 11

Which of the following exonuclease activities is present in DNA polymerase I?

Accepted Answer

A)  3' exonuclease that degrades double stranded DNA
B)  3' exonuclease that degrades hairpin DNA
C)  5' exonuclease that degrades single stranded DNA
D)  5' exonuclease that removes RNA from a DNA-RNA duplex
E)  none of the aboveF) A) and B)
G) A) and C)

Question 12

Which of the following DNA polymerases is correctly defined?

Accepted Answer

A)  polymerase I: DNA repair
B)  polymerase I: RNA primer excision
C)  polymerase II: DNA repair
D)  polymerase III: nucleotide incorporation during replication
E)  all of the aboveF) A) and C)
G) C) and E)

Question 13

Which of the following explains the result of type I topoisomerase activity on underwound DNA, considering that no energy (ATP) is used in the reaction?

Accepted Answer

A)  the linking number is decreased by 1
B)  the linking number is increased by 1
C)  the linking number remains the same but the twist decreases by 1
D)  the linking number remains the same but the twist increases by 1
E)  none of the aboveF) B) and C)
G) B) and E)

Question 14

Type I topoisomerases break _____ strand(s) of DNA; type II topoisomerases break _____strand(s) of DNA. DNA gyrase is a type ___ topoisomerase.

Accepted Answer

A)  both; 1; I
B)  both; 1; I.
C)  both; 1; III
D)  1; both; I
E)  1; both; IIF) D) and E)
G) A) and B) E

Question 15

Show the reaction (with arrow pushing)for addition of the next nucleotide:

Accepted Answer

The answer of Show the reaction (with arrow pushing)for addition...

Question 16

What is an Okazaki fragment?

Accepted Answer

A)  a small section of DNA bound to the leading strand
B)  a small section of DNA bound to the lagging strand
C)  a small section of RNA and DNA bound to the leading strand
D)  a small section of RNA and DNA bound to the lagging strand
E)  none of the aboveF) B) and D)
G) A) and D)

Question 17

In the Klenow fragment of many DNA polymerases, the Mg2+ ions that are required for activity are coordinated to which amino acid R-groups?

Accepted Answer

A)  histidine and aspartate
B)  two aspartates
C)  aspartate and asparagine
D)  aspartate and glutamate
E)  glutamate and glutamineF) B) and D)
G) A) and B) B

Question 18

Which of the following is required for DNA polymerase I activity?

Accepted Answer

A)  3' hydroxyl group
B)  ATP, GTP, TTP and CTP
C)  Zn2+
D)  an RNA template
E)  all of the aboveF) B) and E)
G) B) and D)

Question 19

In eukaryotic replication, which polymerase is analogous to E. coli primase?

Accepted Answer

A)  pol  α\alphaα 
B)  pol  β\betaβ 
C)  pol  γ\gammaγ 
D)  pol  δ\deltaδ 
E)  pol  ε\varepsilonεF) B) and C)
G) None of the above

Question 20

What feature of the telomerase enzyme allows it to synthesize DNA without the use of a DNA or RNA primer?

Accepted Answer

A)  it synthesizes new DNA in a 3' to 5' direction
B)  it contains an RNA oligonucleotide complementary to the telomeric sequence
C)  since the telomeric sequence is a 15 base repeat, it is synthesized separately from the replication process and merely sealed in place by the ligase action of telomerase
D)  telomeric DNA forms a hairpin that is used to create its own complimentary primer
E)  none of the aboveF) A) and B)
G) All of the above

Exam 25: DNA Replication

In a type I topoisomerase, the active site amino acid _________ is covalently bound to the free _______ end of the cut in the DNA.

Correct AnswerverifiedShow Answer

Which of the subunits of DNA polymerase III is responsible for the high processivity of the enzyme?

Correct AnswerverifiedA

A mutation in a gene results in a mutant phenotype. What occurs if the wild-type phenotype is restored by a mutation at another site in the gene?

Correct AnswerverifiedShow Answer

What enzyme that is part of the primosome is responsible for unwinding of the DNA ahead of the replication fork?

Correct AnswerverifiedShow Answer

If a segment of a eukaryotic chromosome contained three origins of replication (at the sites indicated with arrows), how would the segment appear when replication was about half completed?

Correct AnswerverifiedShow Answer

Replication of DNA in E. coli occurs in what type of fashion?

Correct AnswerverifiedShow Answer

Which of the following was evidence that DNA polymerase I was not responsible for the bulk of DNA synthesis in vivo?

Correct AnswerverifiedShow Answer

For the following sequence, indicate the RNA primer that would be needed to start synthesis of the Okazaki fragment. 5'-A-A-C-T-A-G-A-C-C-A-G-A-3'

Correct Answerverified3'-U-U-G-A...View AnswerShow Answer

What protein complexes with ATP and cardiolipin to initiate E. coli DNA replication by creating negative superhelical tension in the double stranded DNA?

Correct AnswerverifiedShow Answer

Which of the following describes the correct sequence of enzyme activity upon the lagging strand?

Correct AnswerverifiedShow Answer

Which of the following exonuclease activities is present in DNA polymerase I?

Correct AnswerverifiedShow Answer

Which of the following DNA polymerases is correctly defined?

Correct AnswerverifiedShow Answer

Which of the following explains the result of type I topoisomerase activity on underwound DNA, considering that no energy (ATP) is used in the reaction?

Correct AnswerverifiedShow Answer

Type I topoisomerases break _____ strand(s) of DNA; type II topoisomerases break _____strand(s) of DNA. DNA gyrase is a type ___ topoisomerase.

Correct AnswerverifiedE

Show the reaction (with arrow pushing)for addition of the next nucleotide:

Correct AnswerverifiedShow Answer

What is an Okazaki fragment?

Correct AnswerverifiedShow Answer

In the Klenow fragment of many DNA polymerases, the Mg2+ ions that are required for activity are coordinated to which amino acid R-groups?

Correct AnswerverifiedB

Which of the following is required for DNA polymerase I activity?

Correct AnswerverifiedShow Answer

In eukaryotic replication, which polymerase is analogous to E. coli primase?

Correct AnswerverifiedShow Answer

What feature of the telomerase enzyme allows it to synthesize DNA without the use of a DNA or RNA primer?

Correct AnswerverifiedShow Answer

In a type I topoisomerase, the active site amino acid ___ is covalently bound to the free _ end of the cut in the DNA.

Correct Answer
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A

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3'-U-U-G-A...
View Answer

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Type I topoisomerases break ___ strand(s) of DNA; type II topoisomerases break _strand(s) of DNA. DNA gyrase is a type _ topoisomerase.

Correct Answer
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E

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In the Klenow fragment of many DNA polymerases, the Mg²⁺ ions that are required for activity are coordinated to which amino acid R-groups?

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B

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