Question 1

After deamination of a cytidine residue in DNA, the new residue will complement with which of the following?

Accepted Answer

A)  Adenosine 
B)  Inosine 
C)  Thymidine 
D)  Guanosine 
E)  Uridine 
A)  Adenosine 
B)  Inosine 
C)  Thymidine 
D)  Guanosine 
E)  Uridine

Question 2

Sunlight is most likely to cause which of the following mutations?

Accepted Answer

A)  interstrand crosslink 
B)  depurination 
C)  deamination 
D)  thymine dimmer 
A)  interstrand crosslink 
B)  depurination 
C)  deamination 
D)  thymine dimmer

Question 3

DNA gyrase

Accepted Answer

A)  introduces positive super twisting into relaxed double- stranded DNA upon the hydrolysis of ATP. 
B)  relaxes negatively supercoiled DNA. 
C)  converts relaxed double-stranded DNA into a negatively supercoiled form upon the hydrolysis ATP. 
D)  relaxes positively supercoiled DNA upon the hydrolysis of ATP 
E)  contains only type I topoisomerase activity. 
A)  introduces positive super twisting into relaxed double- stranded DNA upon the hydrolysis of ATP. 
B)  relaxes negatively supercoiled DNA. 
C)  converts relaxed double-stranded DNA into a negatively supercoiled form upon the hydrolysis ATP. 
D)  relaxes positively supercoiled DNA upon the hydrolysis of ATP 
E)  contains only type I topoisomerase activity.

Question 4

Listed are four enzymes involved in DNA replication1. DNA polymerase III 2. Primase 3. DNA ligase 4. DNA polymerase I. The correct order of action of these enzymes in lagging strand DNA synthesis is

Accepted Answer

A)  4,2,1,3 
B)  2,1,4,3 
C)  4,3,2,1 
D)  2,4,1,3 
E)  4,1,2,3 
A)  4,2,1,3 
B)  2,1,4,3 
C)  4,3,2,1 
D)  2,4,1,3 
E)  4,1,2,3

Question 5

Uracil is occasionally incorporated into DNA during replication. Why is it subsequently removed?

Accepted Answer

A)  The presence of uracil would interfere with parental strand recognition. 
B)  Uracil is unstable and would cause mutations if left in the DNA. 
C)  Uracil makes the same hydrogen bonds as thymine so it might be confused with thymine. 
D)  Cytosine is unstable and occasionally converts to uracil. 
A)  The presence of uracil would interfere with parental strand recognition. 
B)  Uracil is unstable and would cause mutations if left in the DNA. 
C)  Uracil makes the same hydrogen bonds as thymine so it might be confused with thymine. 
D)  Cytosine is unstable and occasionally converts to uracil.

Question 6

DNA replication

Accepted Answer

A)  is bidirectional proceeding from a single initiation point on each chromosome in eukaryotic cells. 
B)  is unidirectional in prokaryotic cells. 
C)  does not require ATP. 
D)  is initiated on RNA primers. 
E)  involves the formation, and not the cleavage, of phosphodiester bonds. 
A)  is bidirectional proceeding from a single initiation point on each chromosome in eukaryotic cells. 
B)  is unidirectional in prokaryotic cells. 
C)  does not require ATP. 
D)  is initiated on RNA primers. 
E)  involves the formation, and not the cleavage, of phosphodiester bonds.

Question 7

The purpose of the short RNA chains which are synthesized during DNA replication is to:

Accepted Answer

A)  code for genes necessary for replication. 
B)  provide a primer for DNA synthesis. 
C)  maintain DNA strands in an open (i.e., not base-paired) from so that polymerases can recognize the template strand. 
D)  reduce superhelical density. 
E)  provide a template for ligation of Okazaki fragments. 
A)  code for genes necessary for replication. 
B)  provide a primer for DNA synthesis. 
C)  maintain DNA strands in an open (i.e., not base-paired) from so that polymerases can recognize the template strand. 
D)  reduce superhelical density. 
E)  provide a template for ligation of Okazaki fragments.

Question 8

The drug AZT (3'-azido-3'-deoxythymidine) inhibits DNA polymerization by:

Accepted Answer

A)  cross_linking DNA strands. 
B)  intercalating into DNA. 
C)  reacting with thymidylate synthase and inactivating it. 
D)  competitively binding to dihydrofolate reductase in place of dihydrofolate. 
E)  terminating DNA chains. 
A)  cross_linking DNA strands. 
B)  intercalating into DNA. 
C)  reacting with thymidylate synthase and inactivating it. 
D)  competitively binding to dihydrofolate reductase in place of dihydrofolate. 
E)  terminating DNA chains.

Question 9

Okazaki fragments are

Accepted Answer

A)  products of leading strand synthesis. 
B)  short single_stranded RNA molecules. 
C)  synthesized by DNA polymerase III. 
D)  excised by DNA polymerase I. 
A)  products of leading strand synthesis. 
B)  short single_stranded RNA molecules. 
C)  synthesized by DNA polymerase III. 
D)  excised by DNA polymerase I.

Question 10

Indicate which of the following is a correct statement about replication.

Accepted Answer

A)  Reverse transcriptase replicates DNA in the to 5' direction. 
B)  Eukaryotic DNA replication proceeds bidirectionally with multiple initiation sites. 
C)  replication of the leading strand within a replicon requires multiple initiation. 
D)  Since there is more DNA in eukaryotes than prokaryotes, the rate of polymerization per growing fork of nucleotides during DNA synthesis in eukaryotes is much greater than in prokaryotes. 
E)  Initiation of DNA replication in prokaryotes occurs randomly throughout the genome. 
A)  Reverse transcriptase replicates DNA in the to 5' direction. 
B)  Eukaryotic DNA replication proceeds bidirectionally with multiple initiation sites. 
C)  replication of the leading strand within a replicon requires multiple initiation. 
D)  Since there is more DNA in eukaryotes than prokaryotes, the rate of polymerization per growing fork of nucleotides during DNA synthesis in eukaryotes is much greater than in prokaryotes. 
E)  Initiation of DNA replication in prokaryotes occurs randomly throughout the genome.

Question 11

Short chains of nucleic acid can be isolated from cells in which DNA is undergoing replication. These segments, known as Okazaki fragments, have which of the following properties?

Accepted Answer

A)  They are double_stranded. 
B)  They are removed by nuclease activity. 
C)  They are DNA_RNA hybrids. 
D)  They arise from the nicking of the sugar_phosphate backbone of the parental DNA chain. 
E)  They contain covalently linked RNA and DNA. 
A)  They are double_stranded. 
B)  They are removed by nuclease activity. 
C)  They are DNA_RNA hybrids. 
D)  They arise from the nicking of the sugar_phosphate backbone of the parental DNA chain. 
E)  They contain covalently linked RNA and DNA.

Question 12

DNA polymerase I

Accepted Answer

A)  nicks DNA to initiate DNA replication. 
B)  has a DNA ligase activity for completing DNA application. 
C)  synthesizes DNA in a > 5' direction. 
D)  requires a primer with a free OH. 
E)  is used only to repair DNA. 
A)  nicks DNA to initiate DNA replication. 
B)  has a DNA ligase activity for completing DNA application. 
C)  synthesizes DNA in a > 5' direction. 
D)  requires a primer with a free OH. 
E)  is used only to repair DNA.

Question 13

Deamination of 5-methylcytosine in DNA is mutagenic because it

Accepted Answer

A)  produces thymine. 
B)  produces uracil. 
C)  changes a base but does not disrupt hydrogen bonding. 
D)  cannot be repaired. 
A)  produces thymine. 
B)  produces uracil. 
C)  changes a base but does not disrupt hydrogen bonding. 
D)  cannot be repaired.

Question 14

Which of the following is a target for base excision repair?

Accepted Answer

A)  deaminated adenine in RNA 
B)  methylated cytosine in DNA 
C)  methylated adenine in RNA 
D)  deaminated cytosine in DNA 
A)  deaminated adenine in RNA 
B)  methylated cytosine in DNA 
C)  methylated adenine in RNA 
D)  deaminated cytosine in DNA

Question 15

DNA polymerase I is extremely accurate in its ability to make a complementary copy of the template. The key activity that allows the polymerase to be so accurate is the

Accepted Answer

A)  polymerase activity. 
B)  5' => exonuclease activity. 
C)  => 5' exonuclease activity. 
D)  reverse transcriptase activity. 
E)  pyrophosphatase activity. 
A)  polymerase activity. 
B)  5' => exonuclease activity. 
C)  => 5' exonuclease activity. 
D)  reverse transcriptase activity. 
E)  pyrophosphatase activity.

Question 16

Helicase

Accepted Answer

A)  unwinds double stranded DNA by breaking base pairs 
B)  will decrease the writhing number of negatively supercoiled DNA 
C)  will increase the linking number of negatively supercoiled DNA 
D)  nicks one strand of double stranded DNA 
E)  cuts both strands of double stranded DNA 
A)  unwinds double stranded DNA by breaking base pairs 
B)  will decrease the writhing number of negatively supercoiled DNA 
C)  will increase the linking number of negatively supercoiled DNA 
D)  nicks one strand of double stranded DNA 
E)  cuts both strands of double stranded DNA

Question 17

A break of a phosphodiester bond in one strand of a double-stranded DNA molecule can be repaired by

Accepted Answer

A)  polynucleotide phosphorylase. 
B)  polynucleotide kinase. 
C)  exonuclease III. 
D)  DNA ligase. 
E)  DNA polymerase. 
A)  polynucleotide phosphorylase. 
B)  polynucleotide kinase. 
C)  exonuclease III. 
D)  DNA ligase. 
E)  DNA polymerase.

Question 18

Which of the following DOES NOT play a role in prokaryotic replication?

Accepted Answer

A)  DNA ligase 
B)  reverse transcriptase 
C)  DNA helicase 
D)  primase 
E)  DNA polymerase I 
A)  DNA ligase 
B)  reverse transcriptase 
C)  DNA helicase 
D)  primase 
E)  DNA polymerase I

Question 19

The base composition of DNA synthesized in the presence of DNA polymerase is dependent upon the

Accepted Answer

A)  molar ratio of deoxyribonucleoside triphosphates in the incubation mixture. 
B)  species of origin of polymerizing enzyme. 
C)  species of origin of the DNA in the incubation mixture. 
D)  the extent of denaturation of the added DNA. 
E)  the presence of specific methylases in the polymerase preparation. 
A)  molar ratio of deoxyribonucleoside triphosphates in the incubation mixture. 
B)  species of origin of polymerizing enzyme. 
C)  species of origin of the DNA in the incubation mixture. 
D)  the extent of denaturation of the added DNA. 
E)  the presence of specific methylases in the polymerase preparation.

Question 20

Indicate which of the following is a correct statement about the process of replication.

Accepted Answer

A)  Only one strand of the DNA duplex is copied. 
B)  Sigma factor is required for recognition of the point at which replication will be initiated. 
C)  The DNA of mammalian chromosomes replicates bidirectionally. 
D)  The only enzyme required for replication is DNA polymerase. 
E)  replication is conservative. 
A)  Only one strand of the DNA duplex is copied. 
B)  Sigma factor is required for recognition of the point at which replication will be initiated. 
C)  The DNA of mammalian chromosomes replicates bidirectionally. 
D)  The only enzyme required for replication is DNA polymerase. 
E)  replication is conservative.

Exam 4: DNA Replication, Recombination, and Repair

After deamination of a cytidine residue in DNA, the new residue will complement with which of the following?

Sunlight is most likely to cause which of the following mutations?

DNA gyrase

Listed are four enzymes involved in DNA replication1. DNA polymerase III 2. Primase 3. DNA ligase 4. DNA polymerase I. The correct order of action of these enzymes in lagging strand DNA synthesis is

Uracil is occasionally incorporated into DNA during replication. Why is it subsequently removed?

DNA replication

The purpose of the short RNA chains which are synthesized during DNA replication is to:

The drug AZT (3'-azido-3'-deoxythymidine) inhibits DNA polymerization by:

Okazaki fragments are

Indicate which of the following is a correct statement about replication.

Short chains of nucleic acid can be isolated from cells in which DNA is undergoing replication. These segments, known as Okazaki fragments, have which of the following properties?

DNA polymerase I

Deamination of 5-methylcytosine in DNA is mutagenic because it

Which of the following is a target for base excision repair?

DNA polymerase I is extremely accurate in its ability to make a complementary copy of the template. The key activity that allows the polymerase to be so accurate is the

Helicase

A break of a phosphodiester bond in one strand of a double-stranded DNA molecule can be repaired by

Which of the following DOES NOT play a role in prokaryotic replication?

The base composition of DNA synthesized in the presence of DNA polymerase is dependent upon the

Indicate which of the following is a correct statement about the process of replication.

Eukaryotic Cell Structure

DNA and RNA: Composition and Structure

Protein I: Composition and Structure

RNA: Transcription and Rna Processing

Protein Synthesis: Translation and Posttranslational Modifications

Recombinant Dna and Biotechnology

Regulation of Gene Expression

Protein II: Structure-Function Relationships in Protein Families

Enzymes: Classification, Kinetics, and Control

The Cytochromes P450 and Nitric Oxide Synthases

Biological Membranes: Structure and Membrane Transport

Fundamentals of Signal Transduction

Bioenergetics and Oxidative Metabolism

Carbohydrate Metabolism I: Major Metabolic Pathways and Their Control

Carbohydrate Metabolism II: Special Pathways and Glycoconjugates

Lipid Metabolism I: Synthesis, Storage, and Utilization of Fatty Acids and Triacylglycerols

Lipid Metabolism II: Pathways of Metabolism of Special Lipids

Amino Acid Metabolism

Purine and Pyrimidine Nucleotide Metabolism

Metabolic Interrelationships

Biochemistry of Hormones

Molecular Cell Biology

Cell Cycle, Programmed Cell Death, and Cancer

Digestion and Absorption of Basic Nutritional Constituents

Digestion and Absorption of Basic Nutritional Constituents

Principles of Nutrition I and II

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