Question 1

The 5' →\rightarrow→ 3' exonuclease activity of E.coli DNA polymerase I is involved in:

Accepted Answer

A)  formation of a nick at the DNA replication origin.
B)  formation of Okazaki fragments.
C)  proofreading of the replication process.
D)  removal of RNA primers by nick translation.
E)  sealing of nicks by ligase action.

Question 2

Match the damage type or repair step at the left with a related enzyme at right.  Only one answer will be the most direct for each.
-excision of a lesion-containing oligonucleotide

Accepted Answer

A)  hypoxanthine-N-glycosylase
B)  AP endonuclease
C)  mutH protein
D)  DNA polymerase I
E)  uracil N-glycosylaseF) mutS-mutL complexG) ABC excinucleaseH) DNA photolyaseI) O6-methylguanine methyltransferaseJ) DNA ligaseK) λ integraseL) RecA proteinM) restriction endonuclease

Question 3

The high fidelity of DNA replication is due primarily to immediate error correction by the 3' -> 5' exonuclease (proofreading)activity of the DNA polymerase.Some incorrectly paired bases escape this proofreading,and further errors can arise from challenges to the chemical integrity of the DNA.List the four classes of repair mechanisms that the cell can use to help correct such errors.

Accepted Answer

The four classes are listed in...

Question 4

In homologous genetic recombination,RecA protein is involved in:

Accepted Answer

A)  formation of Holliday intermediates and branch migration.
B)  introduction of negative supercoils into the recombination products.
C)  nicking the two duplex DNA molecules to initiate the reaction.
D)  pairing a DNA strand from one duplex DNA molecule with sequences in another duplex,regardless of complementarity.
E)  resolution of the Holliday intermediate. A

Question 5

DNA synthesis on the lagging strand in E.coli is a complex process known to involve several proteins.Initiation of a new chain is catalyzed by the enzyme (a)_____________,and elongation is catalyzed by the enzyme (b)______________.Synthesis is discontinuous,yielding short segments called (c)_______________,which are eventually joined by the enzyme (d)______________,which requires the cofactor (e)___________.

Accepted Answer

(a)primase;
(b)DNA ...

Question 6

In base-excision repair,the first enzyme to act is:

Accepted Answer

A)  AP endonuclease.
B)  Dam methylase.
C)  DNA glycosylase.
D)  DNA ligase.
E)  DNA polymerase.

Question 7

A suitable substrate for DNA polymerase is shown below.Label the primer and template,and indicate which end of each strand must be 3' or 5'.  To observe DNA synthesis on this substrate in vitro,what additional reaction components must be added?

Accepted Answer

The top strand (the primer)has its 5' en...

Question 8

List three types of DNA damage that require repair.

Accepted Answer

The defects in DNA that require repair include 
(a)mismatches that occur during replication; 
(b)abnormal bases; 
(c)pyrimidine dimers produced by UV irradiation.Other answers are possible.

Question 9

Which mechanism is used to repair a thymidine dimer in DNA?

Accepted Answer

A)  Mismatch repair
B)  Base-excision repair
C)  Nucleotide-excision repair
D)  Direct repair
E)  More than one is used for this type of lesion

Question 10

The role of the Dam methylase is to:

Accepted Answer

A)  add a methyl group to uracil,converting it to thymine.
B)  modify the template strand for recognition by repair systems.
C)  remove a methyl group from thymine.
D)  remove a mismatched nucleotide from the template strand.
E)  replace a mismatched nucleotide with the correct one.

Question 11

Briefly describe the role of recombination in the generation of antibody (immunoglobin)diversity.

Accepted Answer

The genes for immunoglobin polypeptide c...

Question 12

An Okazaki fragment is a:

Accepted Answer

A)  fragment of DNA resulting from endonuclease action.
B)  fragment of RNA that is a subunit of the 30S ribosome.
C)  piece of DNA that is synthesized in the 3'  →\rightarrow→ 5' direction.
D)  segment of DNA that is an intermediate in the synthesis of the lagging strand.
E)  segment of mRNA synthesized by RNA polymerase.

Question 13

Which of the following is not a feature of homologous recombination during meiosis?

Accepted Answer

A)  A double strand break
B)  Cleavage of two crossover events
C)  Alignment of homologous chromosomes
D)  Formation of a single Holliday intermediate
E)  Exposed 3' ends invade the intact duplex DNA of the homolog

Question 14

Prokaryotic DNA polymerase III:

Accepted Answer

A)  contains a 5'  →\rightarrow→   3' proofreading activity to improve the fidelity of replication.
B)  does not require a primer molecule to initiate replication.
C)  has a  β\betaβ  subunit that acts as a circular clamp to improve the processivity of DNA synthesis.
D)  synthesizes DNA in the 3'  →\rightarrow→   5' direction.
E)  synthesizes only the leading strand;DNA polymerase I synthesizes the lagging strand.

Question 15

Which of the following is not required for initiation of DNA replication in E.coli?

Accepted Answer

A)  DnaB (helicase) 
B)  DnaG (primase) 
C)  Dam methylase
D)  DNA ligase
E)  DnaA (a AAA+ ATPase)

Question 16

Which of the following statements is false? In vitro,the strand-exchange reaction:

Accepted Answer

A)  can include formation of a Holliday intermediate.
B)  is accompanied by ATP hydrolysis.
C)  may involve transient formation of a three- or four-stranded DNA complex.
D)  needs RecA protein.
E)  requires DNA polymerase.

Question 17

Which one of the following statements about enzymes that interact with DNA is true?

Accepted Answer

A)  
E)  coli DNA polymerase I is unusual in that it possesses only a 5'  →\rightarrow→ 3' exonucleolytic activity.
B)  Endonucleases degrade circular but not linear DNA molecules.
C)  Exonucleases degrade DNA at a free end.
D)  Many DNA polymerases have a proofreading 5'  →\rightarrow→  3' exonuclease.
E)  Primases synthesize a short stretch of DNA to prime further synthesis.  C

Question 18

Briefly explain the difference between base-excision repair and nucleotide-excision repair.

Accepted Answer

Base excision involves removing only the...

Question 19

Briefly describe the biochemical role of the following enzymes in DNA replication in E.coli:
(a)DNA helicase; 
(b)primase; 
(c)the 3' $\rightarrow$ 5' exonuclease activity of DNA polymerase; 
(d)DNA 1igase; 
(e)topoisomerases;
 (f)the 5' $\rightarrow$ 3' exonuclease activity of DNA polymerase I.

Accepted Answer

(a)Helicase unwinds double-stranded DNA ...

Question 20

In a mammalian cell,DNA repair systems:

Accepted Answer

A)  are extraordinarily efficient energetically.
B)  are generally absent,except in egg and sperm cells.
C)  can repair deletions,but not mismatches.
D)  can repair most types of lesions except those caused by UV light.
E)  normally repair more than 99% of the DNA lesions that occur.

Exam 25: Dna Metabolism

The 5' $\rightarrow$ 3' exonuclease activity of E.coli DNA polymerase I is involved in:

Correct Answer
verified

Match the damage type or repair step at the left with a related enzyme at right. Only one answer will be the most direct for each. -excision of a lesion-containing oligonucleotide

Correct Answer
verified

Correct Answer
verified
The four classes are listed in...
View Answer

In homologous genetic recombination,RecA protein is involved in:

Correct Answer
verified
A

Correct Answer
verified
(a)primase;
(b)DNA ...
View Answer

In base-excision repair,the first enzyme to act is:

Correct Answer
verified

A suitable substrate for DNA polymerase is shown below.Label the primer and template,and indicate which end of each strand must be 3' or 5'. To observe DNA synthesis on this substrate in vitro,what additional reaction components must be added?

Correct Answer
verified
The top strand (the primer)has its 5' en...
View Answer

List three types of DNA damage that require repair.

Correct Answer
verified
The defects in DNA that require repair include (a)mismatches that occur during replication; (b)abnormal bases; (c)pyrimidine dimers produced by UV irradiation.Other answers are possible.

Which mechanism is used to repair a thymidine dimer in DNA?

Correct Answer
verified

The role of the Dam methylase is to:

Correct Answer
verified

Briefly describe the role of recombination in the generation of antibody (immunoglobin)diversity.

Correct Answer
verified
The genes for immunoglobin polypeptide c...
View Answer

An Okazaki fragment is a:

Correct Answer
verified

Which of the following is not a feature of homologous recombination during meiosis?

Correct Answer
verified

Prokaryotic DNA polymerase III:

Correct Answer
verified

Which of the following is not required for initiation of DNA replication in E.coli?

Correct Answer
verified

Which of the following statements is false? In vitro,the strand-exchange reaction:

Correct Answer
verified

Which one of the following statements about enzymes that interact with DNA is true?

Correct Answer
verified
C

Briefly explain the difference between base-excision repair and nucleotide-excision repair.

Correct Answer
verified
Base excision involves removing only the...
View Answer

Briefly describe the biochemical role of the following enzymes in DNA replication in E.coli: (a)DNA helicase; (b)primase; (c)the 3' $\rightarrow$ 5' exonuclease activity of DNA polymerase; (d)DNA 1igase; (e)topoisomerases; (f)the 5' $\rightarrow$ 3' exonuclease activity of DNA polymerase I.

Correct Answer
verified
(a)Helicase unwinds double-stranded DNA ...
View Answer

In a mammalian cell,DNA repair systems:

Correct Answer
verified

Exam 25: Dna Metabolism

The 5' →\rightarrow→ 3' exonuclease activity of E.coli DNA polymerase I is involved in:

Correct AnswerverifiedShow Answer

Match the damage type or repair step at the left with a related enzyme at right. Only one answer will be the most direct for each. -excision of a lesion-containing oligonucleotide

Correct AnswerverifiedShow Answer

Correct AnswerverifiedThe four classes are listed in...View AnswerShow Answer

In homologous genetic recombination,RecA protein is involved in:

Correct AnswerverifiedA

Correct Answerverified(a)primase; (b)DNA ...View AnswerShow Answer

In base-excision repair,the first enzyme to act is:

Correct AnswerverifiedShow Answer

A suitable substrate for DNA polymerase is shown below.Label the primer and template,and indicate which end of each strand must be 3' or 5'. To observe DNA synthesis on this substrate in vitro,what additional reaction components must be added?

Correct AnswerverifiedThe top strand (the primer)has its 5' en...View AnswerShow Answer

List three types of DNA damage that require repair.

Correct AnswerverifiedThe defects in DNA that require repair include (a)mismatches that occur during replication; (b)abnormal bases; (c)pyrimidine dimers produced by UV irradiation.Other answers are possible.

Which mechanism is used to repair a thymidine dimer in DNA?

Correct AnswerverifiedShow Answer

The role of the Dam methylase is to:

Correct AnswerverifiedShow Answer

Briefly describe the role of recombination in the generation of antibody (immunoglobin)diversity.

Correct AnswerverifiedThe genes for immunoglobin polypeptide c...View AnswerShow Answer

An Okazaki fragment is a:

Correct AnswerverifiedShow Answer

Which of the following is not a feature of homologous recombination during meiosis?

Correct AnswerverifiedShow Answer

Prokaryotic DNA polymerase III:

Correct AnswerverifiedShow Answer

Which of the following is not required for initiation of DNA replication in E.coli?

Correct AnswerverifiedShow Answer

Which of the following statements is false? In vitro,the strand-exchange reaction:

Correct AnswerverifiedShow Answer

Which one of the following statements about enzymes that interact with DNA is true?

Correct AnswerverifiedC

Briefly explain the difference between base-excision repair and nucleotide-excision repair.

Correct AnswerverifiedBase excision involves removing only the...View AnswerShow Answer

Briefly describe the biochemical role of the following enzymes in DNA replication in E.coli: (a)DNA helicase; (b)primase; (c)the 3' →\rightarrow→ 5' exonuclease activity of DNA polymerase; (d)DNA 1igase; (e)topoisomerases; (f)the 5' →\rightarrow→ 3' exonuclease activity of DNA polymerase I.

Correct Answerverified(a)Helicase unwinds double-stranded DNA ...View AnswerShow Answer

In a mammalian cell,DNA repair systems:

Correct AnswerverifiedShow Answer

The 5' $\rightarrow$ 3' exonuclease activity of E.coli DNA polymerase I is involved in:

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
The four classes are listed in...
View Answer

Correct Answer
verified
A

Correct Answer
verified
(a)primase;
(b)DNA ...
View Answer

Correct Answer
verified

Correct Answer
verified
The top strand (the primer)has its 5' en...
View Answer

Correct Answer
verified
The defects in DNA that require repair include (a)mismatches that occur during replication; (b)abnormal bases; (c)pyrimidine dimers produced by UV irradiation.Other answers are possible.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
The genes for immunoglobin polypeptide c...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
C

Correct Answer
verified
Base excision involves removing only the...
View Answer

Briefly describe the biochemical role of the following enzymes in DNA replication in E.coli: (a)DNA helicase; (b)primase; (c)the 3' $\rightarrow$ 5' exonuclease activity of DNA polymerase; (d)DNA 1igase; (e)topoisomerases; (f)the 5' $\rightarrow$ 3' exonuclease activity of DNA polymerase I.

Correct Answer
verified
(a)Helicase unwinds double-stranded DNA ...
View Answer

Correct Answer
verified