Question 1

Okazaki fragments are

Accepted Answer

A)  short DNA pieces that explain how DNA is synthesized on the lagging strand. 
B)  short DNA pieces that explain how DNA is synthesized on the leading strand. 
C)  the remnants of the original strands that are dispersed in the new double stranded DNA molecules 
D)  RNA primers used for DNA replication. 
A)  short DNA pieces that explain how DNA is synthesized on the lagging strand. 
B)  short DNA pieces that explain how DNA is synthesized on the leading strand. 
C)  the remnants of the original strands that are dispersed in the new double stranded DNA molecules 
D)  RNA primers used for DNA replication.

Question 2

The famous Meselson and Stahl experiment showed:

Accepted Answer

A)  DNA is replicated by a semi-conservative mechanism. 
B)  The direction of DNA synthesis proceeds 5' → 3'. 
C)  The isotope 15N is denser than 14N. 
D)  DNA replication is semi-conservative and 15N is denser than 14N. 
E)  All of these are correct. 
A)  DNA is replicated by a semi-conservative mechanism. 
B)  The direction of DNA synthesis proceeds 5' → 3'. 
C)  The isotope 15N is denser than 14N. 
D)  DNA replication is semi-conservative and 15N is denser than 14N. 
E)  All of these are correct.

Question 3

Suppose Meselson & Stahl had observed the following data in their famous experiment involving a switch from medium containing 15N to 14N. What would they have concluded about the nature of DNA replication?

Accepted Answer

A)  They still would have concluded that DNA replication is semiconservative, i.e., each double helix contains one parental strand and one newly synthesized strand. 
B)  They would have concluded that DNA replication is conservative, i.e., one double helix contains only the parental strands, while the other contains only newly synthesized DNA. 
C)  They would have concluded that DNA replication is dispersive/random, i.e., each strand of each double helix contains a mixture of parental and newly synthesized sequences. 
D)  They would have been unable to distinguish which is correct. 
A)  They still would have concluded that DNA replication is semiconservative, i.e., each double helix contains one parental strand and one newly synthesized strand. 
B)  They would have concluded that DNA replication is conservative, i.e., one double helix contains only the parental strands, while the other contains only newly synthesized DNA. 
C)  They would have concluded that DNA replication is dispersive/random, i.e., each strand of each double helix contains a mixture of parental and newly synthesized sequences. 
D)  They would have been unable to distinguish which is correct.

Question 4

If replication were conservative instead of semi-conservative, the famous Meselson and Stahl experiment would have shown which of the following results after the first round of replication?

Accepted Answer

A)  All of the double helices would have been heavy chains 
B)  All of the double helices would have been light chains 
C)  Half of the double helices would have been all heavy chains and the other half would have been all light chains 
D)  All of the double helices would have been a combination of a heavy strand and a light strand 
A)  All of the double helices would have been heavy chains 
B)  All of the double helices would have been light chains 
C)  Half of the double helices would have been all heavy chains and the other half would have been all light chains 
D)  All of the double helices would have been a combination of a heavy strand and a light strand

Question 5

Which of the activities of DNA Polymerase I is most important in removing the primer?

Accepted Answer

A)  Polymerase activity. 
B)  Ability to nick intact double stranded DNA. 
C)  5' → 3' exonuclease. 
D)  3' → 5' exonuclease. 
E)  None of these is used for primer removal. 
A)  Polymerase activity. 
B)  Ability to nick intact double stranded DNA. 
C)  5' → 3' exonuclease. 
D)  3' → 5' exonuclease. 
E)  None of these is used for primer removal.

Question 6

Recombination:

Accepted Answer

A)  occurs randomly throughout a chromosome 
B)  occurs more often in areas called hot spots 
C)  is a process that only happens under controlled laboratory conditions 
D)  is a spontaneous process that requires no enzymes 
A)  occurs randomly throughout a chromosome 
B)  occurs more often in areas called hot spots 
C)  is a process that only happens under controlled laboratory conditions 
D)  is a spontaneous process that requires no enzymes

Question 7

When the synthesis of new DNA is directed by an original template DNA molecule

Accepted Answer

A)  the DNA produced has two newly formed strands (no change in the original DN
A)  
B)  two DNA molecules are formed, each with one new strand and one strand from the original DNA 
C)  there is random arrangement of newly formed and original DNA on the two strands of the DNA produced 
D)  no information is available on this subject 
A)  the DNA produced has two newly formed strands (no change in the original DN
A)  
B)  two DNA molecules are formed, each with one new strand and one strand from the original DNA 
C)  there is random arrangement of newly formed and original DNA on the two strands of the DNA produced 
D)  no information is available on this subject

Question 8

The enzyme that attaches the Okazaki fragments together is called

Accepted Answer

A)  ligase. 
B)  primase. 
C)  DNA polymerase I 
D)  DNA polymerase III 
A)  ligase. 
B)  primase. 
C)  DNA polymerase I 
D)  DNA polymerase III

Question 9

A special protein called proliferating cell nuclear antigen serves the purpose of the clamp in eukaryotes.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following is NOT an observed event in the flow of genetic information?

Accepted Answer

A)  DNA --> RNA 
B)  RNA --> DNA 
C)  RNA --> RNA 
D)  DNA --> DNA 
E)  RNA --> Protein
F) Protein --> RNA
G) All of the choices ARE observed 
A)  DNA --> RNA 
B)  RNA --> DNA 
C)  RNA --> RNA 
D)  DNA --> DNA 
E)  RNA --> Protein
F) Protein --> RNA
G) All of the choices ARE observed

Question 11

One major difficulty in replicating linear DNA molecules is replacing the segment of DNA occupied by the RNA primer on the telomeres at the ends of the DNA.

Accepted Answer

A) True 
 B)False

Question 12

In order to replicate both strands, E. coli

Accepted Answer

A)  displaces one of the strands and folds it back so both strands face in the same direction, so they can be synthesized at once. 
B)  synthesizes each strand in the opposite direction (one 5' → 3', one 3' → 5'), so they can be synthesized at once. 
C)  only synthesizes one strand at a time. 
A)  displaces one of the strands and folds it back so both strands face in the same direction, so they can be synthesized at once. 
B)  synthesizes each strand in the opposite direction (one 5' → 3', one 3' → 5'), so they can be synthesized at once. 
C)  only synthesizes one strand at a time.

Question 13

Repair of DNA is usually carried out by

Accepted Answer

A)  hydrolysis of the entire damaged DNA molecule and synthesis of new DNA 
B)  hydrolysis of one strand of the damaged DNA molecule and synthesis of a new strand 
C)  a cut-and patch process 
D)  introducing additional supercoiling in the molecule 
A)  hydrolysis of the entire damaged DNA molecule and synthesis of new DNA 
B)  hydrolysis of one strand of the damaged DNA molecule and synthesis of a new strand 
C)  a cut-and patch process 
D)  introducing additional supercoiling in the molecule

Question 14

Ultra-violet light principally causes which of the following damages to DNA?

Accepted Answer

A)  mismatches between stands 
B)  breaks in the phosphodiester backbone of the DNA strand 
C)  thymine dimerization 
D)  methylation of specific bases 
A)  mismatches between stands 
B)  breaks in the phosphodiester backbone of the DNA strand 
C)  thymine dimerization 
D)  methylation of specific bases

Question 15

One of the most important ways in which DNA is modified after synthesis is

Accepted Answer

A)  methylation of bases 
B)  covalent binding of proteins to the sugar moieties 
C)  splicing of RNA "leaders" 
D)  electrostatic binding of negatively charged counterions 
A)  methylation of bases 
B)  covalent binding of proteins to the sugar moieties 
C)  splicing of RNA "leaders" 
D)  electrostatic binding of negatively charged counterions

Question 16

A prokaryotic replisome typically contains three molecules of DNA pol III, but only one molecule of DNA pol I. Why?

Accepted Answer

A)  The DNA pol I works on the leading strand, while DNA pol IIIs work on the Okazaki fragments. since there are several of those, it takes more proteins to keep up. 
B)  DNA pol I has a built-in proofreading exonuclease; DNA pol III does not. The second DNA pol III is needed to follow the first to accomplish the necessary proofreading. 
C)  The DNA pol IIIs do most of the work. DNA pol I only has to work on the telomers. 
D)  DNA pol I replaces the RNA primers with DNA, which really only needs to be done repetitively on one strand, while both strands are worked on by the DNA pol IIIs. 
A)  The DNA pol I works on the leading strand, while DNA pol IIIs work on the Okazaki fragments. since there are several of those, it takes more proteins to keep up. 
B)  DNA pol I has a built-in proofreading exonuclease; DNA pol III does not. The second DNA pol III is needed to follow the first to accomplish the necessary proofreading. 
C)  The DNA pol IIIs do most of the work. DNA pol I only has to work on the telomers. 
D)  DNA pol I replaces the RNA primers with DNA, which really only needs to be done repetitively on one strand, while both strands are worked on by the DNA pol IIIs.

Question 17

Which repair mechanism has an intermediate wherein a region of single-stranded DNA is temporarily created?

Accepted Answer

A)  Base Excision 
B)  Nucleotide Excision 
C)  Pol III Proofreading 
D)  Mismatch Repair 
A)  Base Excision 
B)  Nucleotide Excision 
C)  Pol III Proofreading 
D)  Mismatch Repair

Question 18

Semiconservative replication of DNA was established experimentally by

Accepted Answer

A)  gel electrophoresis. 
B)  ultraviolet spectroscopy. 
C)  column chromatography. 
D)  density-gradient centrifugation. 
A)  gel electrophoresis. 
B)  ultraviolet spectroscopy. 
C)  column chromatography. 
D)  density-gradient centrifugation.

Question 19

It is so important to keep the DNA molecule fully connected that some repair mechanisms will actually allow mismatches or deletions from the DNA.

Accepted Answer

A) True 
 B)False

Question 20

Replication of eukaryotic DNA

Accepted Answer

A)  must occur faster than replication of prokaryotic DNA 
B)  must be controlled to coordinate with the cell cycle 
C)  takes place during mitosis 
D)  takes place twice during each cell cycle 
A)  must occur faster than replication of prokaryotic DNA 
B)  must be controlled to coordinate with the cell cycle 
C)  takes place during mitosis 
D)  takes place twice during each cell cycle

Exam 10: Biosynthesis of Nucleic Acids: Replication

Okazaki fragments are

The famous Meselson and Stahl experiment showed:

Suppose Meselson & Stahl had observed the following data in their famous experiment involving a switch from medium containing 15N to 14N. What would they have concluded about the nature of DNA replication?

If replication were conservative instead of semi-conservative, the famous Meselson and Stahl experiment would have shown which of the following results after the first round of replication?

Which of the activities of DNA Polymerase I is most important in removing the primer?

Recombination:

When the synthesis of new DNA is directed by an original template DNA molecule

The enzyme that attaches the Okazaki fragments together is called

A special protein called proliferating cell nuclear antigen serves the purpose of the clamp in eukaryotes.

Which of the following is NOT an observed event in the flow of genetic information?

One major difficulty in replicating linear DNA molecules is replacing the segment of DNA occupied by the RNA primer on the telomeres at the ends of the DNA.

In order to replicate both strands, E. coli

Repair of DNA is usually carried out by

Ultra-violet light principally causes which of the following damages to DNA?

One of the most important ways in which DNA is modified after synthesis is

A prokaryotic replisome typically contains three molecules of DNA pol III, but only one molecule of DNA pol I. Why?

Which repair mechanism has an intermediate wherein a region of single-stranded DNA is temporarily created?

Semiconservative replication of DNA was established experimentally by

It is so important to keep the DNA molecule fully connected that some repair mechanisms will actually allow mismatches or deletions from the DNA.

Replication of eukaryotic DNA

Biochemistry and the Organization of Cells

Water: the Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three-Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins: Enzymes

The Behavior of Proteins: Enzymes, Mechanisms, and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids: How Structure Conveys Information

Transcription of the Genetic Code: Biosynthesis of RNA

Protein Synthesis: Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses, Cancer, and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism: Cellular Signaling

Filters

Suppose Meselson & Stahl had observed the following data in their famous experiment involving a switch from medium containing ¹⁵N to ¹⁴N. What would they have concluded about the nature of DNA replication?