Question 1

Deaminated bases must be removed from DNA because

Accepted Answer

A)  they distort the molecule. 
B)  they form thymine dimers. 
C)  they pair incorrectly during replication. 
D)  the mRNA formed may be irregular. 
A)  they distort the molecule. 
B)  they form thymine dimers. 
C)  they pair incorrectly during replication. 
D)  the mRNA formed may be irregular. C

Question 2

How many replisomes are required for one complete round of DNA replication in E. coli?

Accepted Answer

A)  one 
B)  two 
C)  four 
D)  more than 4 
A)  one 
B)  two 
C)  four 
D)  more than 4 B

Question 3

How are the BRCA proteins and their genes implicated in breast cancer?

Accepted Answer

A)  The BRCA proteins damage DNA by generating double-stranded breaks which can lead to cancer. 
B)  Cells become more susceptible to damage if the genes for these proteins are damaged. 
C)  BRCA proteins inhibit excision repair mechanisms. 
D)  BRCA proteins initiate recombination between non-homologous DNA sequences. 
A)  The BRCA proteins damage DNA by generating double-stranded breaks which can lead to cancer. 
B)  Cells become more susceptible to damage if the genes for these proteins are damaged. 
C)  BRCA proteins inhibit excision repair mechanisms. 
D)  BRCA proteins initiate recombination between non-homologous DNA sequences. B

Question 4

In E. coli replication begins at the origin of replication and proceeds in one direction until the entire circular DNA molecule has been copied.

Accepted Answer

A) True 
 B)False

Question 5

In photoreactivation, DNA damage caused by UV light is reversed by DNA photolyase which

Accepted Answer

A)  is activated by UV light to form a complex. 
B)  removes nicks in the DNA backbone. 
C)  forms a complex with thymine dimers which absorbs visible light and reverses the dimerization. 
D)  binds to the adenine bases opposite the thymine dimer. 
E)  All of the above 
A)  is activated by UV light to form a complex. 
B)  removes nicks in the DNA backbone. 
C)  forms a complex with thymine dimers which absorbs visible light and reverses the dimerization. 
D)  binds to the adenine bases opposite the thymine dimer. 
E)  All of the above

Question 6

What is the function of the primosome?

Accepted Answer

A)  Removal of RNA from the lagging strand. 
B)  Synthesis of short RNA fragments. 
C)  Assembly of DNA polymerase III holoenzyme. 
D)  Detection of the origin of replication. 
A)  Removal of RNA from the lagging strand. 
B)  Synthesis of short RNA fragments. 
C)  Assembly of DNA polymerase III holoenzyme. 
D)  Detection of the origin of replication.

Question 7

In DNA repair, DNA glycosylases recognize deaminated bases within the DNA polymer and remove the deaminated

Accepted Answer

A)  nucleoside. 
B)  nucleotide. 
C)  thymine dimers. 
D)  bases. 
A)  nucleoside. 
B)  nucleotide. 
C)  thymine dimers. 
D)  bases.

Question 8

What is the DNA sequence 5ʹ → 3ʹ) determined in this gel? Assume the samples were applied near the top of the gel.

Accepted Answer

A)  AGGCTGGACGA 
B)  AGGGGCTAGCA 
C)  AGGCTGACGGA 
D)  AGGCAGTCGGA 
A)  AGGCTGGACGA 
B)  AGGGGCTAGCA 
C)  AGGCTGACGGA 
D)  AGGCAGTCGGA

Question 9

Since deamination is a common cause of DNA damage, and since the deamination of cytosine forms a product similar in structure to uracil, repair enzymes cannot repair this damage easily.

Accepted Answer

A) True 
 B)False

Question 10

The general excision repair pathway for DNA repair has the following order:

Accepted Answer

A)  endonuclease cuts → helicase or endonuclease removes → DNA polymerase → DNA ligase 
B)  DNA ligase → DNA polymerase → helicase or endonuclease removes → endonuclease cuts 
C)  endonuclease cuts → DNA polymerase repairs → helicase opens up → DNA ligase 
D)  endonuclease cuts → DNA ligase removes → endonuclease removes → DNA ligase 
A)  endonuclease cuts → helicase or endonuclease removes → DNA polymerase → DNA ligase 
B)  DNA ligase → DNA polymerase → helicase or endonuclease removes → endonuclease cuts 
C)  endonuclease cuts → DNA polymerase repairs → helicase opens up → DNA ligase 
D)  endonuclease cuts → DNA ligase removes → endonuclease removes → DNA ligase

Question 11

The purpose of SSB is to prevent single-stranded DNA from folding back on itself to form double-helical regions.

Accepted Answer

A) True 
 B)False

Question 12

Meselson and Stahlʹs experiments involved growing E. coli on a medium containing 15N heavy nitrogen) which increased the density of the bacterial DNA. Cells were then grown on a medium containing only 14N. DNA samples were obtained for analysis after one, two and three rounds of replication generations) and centrifuged on a density gradient. The double-helical DNA forms bands in the gradient depending on its density. How many bands did Meselson and Stahl see after two generation of cells were grown on the 14N medium?

Accepted Answer

A)  One with DNA containing both 15N and 14N. 
B)  Two, one with DNA containing only 15N and one with DNA containing only 14N. 
C)  Two, one with DNA containing both 15N and 14N and one with DNA containing only 14N. 
D)  Three, one with DNA containing only 15N, one with DNA containing both 15N and 14N and one with DNA containing only 14N. 
A)  One with DNA containing both 15N and 14N. 
B)  Two, one with DNA containing only 15N and one with DNA containing only 14N. 
C)  Two, one with DNA containing both 15N and 14N and one with DNA containing only 14N. 
D)  Three, one with DNA containing only 15N, one with DNA containing both 15N and 14N and one with DNA containing only 14N.

Question 13

Eukaryotic cells contain at least five DNA polymerases all of which are responsible for nuclear DNA replication.

Accepted Answer

A) True 
 B)False

Question 14

E. coli DNA polymerase catalyzes polymerization in the directions).

Accepted Answer

A)  5ʹ → 3ʹ 
B)  3ʹ → 5ʹ 
C)  2ʹ → 5ʹ 
D)  both 5ʹ → 3ʹ and 3ʹ → 5ʹ 
E)  All of the above 
A)  5ʹ → 3ʹ 
B)  3ʹ → 5ʹ 
C)  2ʹ → 5ʹ 
D)  both 5ʹ → 3ʹ and 3ʹ → 5ʹ 
E)  All of the above

Question 15

DNA fingerprinting is possible for identification because each person accumulates over a hundred mutations during his or her lifetime.

Accepted Answer

A) True 
 B)False

Question 16

The replication of DNA is because .

Accepted Answer

A)  conservative; one strand of parental DNA is retained in each daughter DNA 
B)  conservative; each daughter molecule has two new strands copied from the parental DNA template 
C)  semiconservative; one strand of parental DNA is retained in each daughter DNA 
D)  semiconservative; each daughter molecule has two new strands copied from the parental DNA template 
A)  conservative; one strand of parental DNA is retained in each daughter DNA 
B)  conservative; each daughter molecule has two new strands copied from the parental DNA template 
C)  semiconservative; one strand of parental DNA is retained in each daughter DNA 
D)  semiconservative; each daughter molecule has two new strands copied from the parental DNA template

Question 17

DNA polymerase I which is inhibited by dideoxynucleoside triphosphates is used in the Sanger method for DNA sequencing.

Accepted Answer

A) True 
 B)False

Question 18

The polymerization of DNA is essentially irreversible due to the hydrolysis of pyrophosphate.

Accepted Answer

A) True 
 B)False

Question 19

The β subunits of E. coli DNA polymerase form a sliding clamp that surrounds the DNA strands at the replication fork.

Accepted Answer

A) True 
 B)False

Question 20

The main difference between prokaryotic and eukaryotic DNA replication mechanisms is

Accepted Answer

A)  no Okazaki fragments are made in eukaryotes. 
B)  both leading and lagging strands are continuous in eukaryotes. 
C)  no primer synthesis is needed in eukaryotes. 
D)  the replication fork moves slower in eukaryotes. 
A)  no Okazaki fragments are made in eukaryotes. 
B)  both leading and lagging strands are continuous in eukaryotes. 
C)  no primer synthesis is needed in eukaryotes. 
D)  the replication fork moves slower in eukaryotes.

Exam 20: Dna Replication, Repair, and Recombination

Deaminated bases must be removed from DNA because

How many replisomes are required for one complete round of DNA replication in E. coli?

How are the BRCA proteins and their genes implicated in breast cancer?

In E. coli replication begins at the origin of replication and proceeds in one direction until the entire circular DNA molecule has been copied.

In photoreactivation, DNA damage caused by UV light is reversed by DNA photolyase which

What is the function of the primosome?

In DNA repair, DNA glycosylases recognize deaminated bases within the DNA polymer and remove the deaminated

What is the DNA sequence 5ʹ → 3ʹ) determined in this gel? Assume the samples were applied near the top of the gel.

Since deamination is a common cause of DNA damage, and since the deamination of cytosine forms a product similar in structure to uracil, repair enzymes cannot repair this damage easily.

The general excision repair pathway for DNA repair has the following order:

The purpose of SSB is to prevent single-stranded DNA from folding back on itself to form double-helical regions.

Eukaryotic cells contain at least five DNA polymerases all of which are responsible for nuclear DNA replication.

E. coli DNA polymerase catalyzes polymerization in the directions).

DNA fingerprinting is possible for identification because each person accumulates over a hundred mutations during his or her lifetime.

The replication of DNA is because .

DNA polymerase I which is inhibited by dideoxynucleoside triphosphates is used in the Sanger method for DNA sequencing.

The polymerization of DNA is essentially irreversible due to the hydrolysis of pyrophosphate.

The β subunits of E. coli DNA polymerase form a sliding clamp that surrounds the DNA strands at the replication fork.

The main difference between prokaryotic and eukaryotic DNA replication mechanisms is

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

Transcription and Rna Processing

Protein Synthesis

Recombinant Dna Technology

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