Question 1

In contrast to bacteria,eukaryotic chromosomes need multiple DNA replication origins because:

Accepted Answer

A)  eukaryotic chromosomes cannot usually replicate bidirectionally.
B)  eukaryotic genomes are not usually circular,like the bacterial chromosome is.
C)  the processivity of the eukaryotic DNA polymerase is much less than the bacterial enzyme.
D)  their replication rate is much slower,and it would take too long with only a single origin per chromosome.
E)  they have a variety of DNA polymerases for different purposes,and need a corresponding variety of replication origins.F) A) and C)
G) C) and D)

Question 2

List two proteins or enzymes,other than DNA polymerase III,that are found at the replication fork in E.coli.Describe each of their functions with no more than one sentence.

Accepted Answer

The proteins are listed in Table 25-4.Th...

Question 3

Which mechanism is used to repair a chemically modified base 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 lesionF) A) and E)
G) D) and E)

Question 4

Outline the key steps that occur during meiosis in animal germ-line cells.

Accepted Answer

The chromosomes of a diploid cell are du...

Question 5

All known DNA polymerases can only elongate a preexisting DNA chain (i.e. ,require a primer)but cannot initiate a new DNA chain.Nevertheless,during semiconservative DNA replication in the cell,entirely new daughter DNA chains are synthesized.Explain the process that occurs in the cell that allows for the synthesis of daughter chains by DNA polymerase.

Accepted Answer

In the cell,initiation of DNA chains occ...

Question 6

The Ames test is used to:

Accepted Answer

A)  detect bacterial viruses.
B)  determine the rate of DNA replication.
C)  examine the potency of antibiotics.
D)  measure the mutagenic effects of various chemical compounds.
E)  quantify the damaging effects of UV light on DNA molecules.F) D) and E)
G) A) and B)

Question 7

In the bacterial cell,what are catenated chromosomes,when do they arise,and how does the cell resolve the problem posed by their structure?

Accepted Answer

Catenanes are topologically interlinked ...

Question 8

What distinguishes the two mechanistic pathways for transposition in bacteria,and what is a cointegrate?

Accepted Answer

Direct transposition moves the transposo...

Question 9

In homologous recombination in E.coli,the protein that moves along a double-stranded DNA,unwinding the strands ahead of it and degrading them,is:

Accepted Answer

A)  chi.
B)  DNA ligase.
C)  RecA protein.
D)  RecBCD enzyme.
E)  RuvC protein (resolvase) .F) C) and E)
G) B) and C)

Question 10

Explain the role of DNA glycosylases in DNA repair.

Accepted Answer

When spontaneous deamination converts cy...

Question 11

What is an Okazaki fragment? What enzyme(s)is (are)required for its formation in E.coli?

Accepted Answer

An Okazaki fragment is an intermediate i...

Question 12

The ABC excinuclease is essential in:

Accepted Answer

A)  base-excision repair.
B)  methyl-directed repair.
C)  mismatch repair.
D)  nucleotide-excision repair.
E)  SOS repair.F) B) and C)
G) A) and E)

Question 13

Explain how inheriting mutations in genes encoding DNA repair enzymes could lead to increased cancer risk.

Accepted Answer

Mutations in DNA repair genes ...

Question 14

When bacterial DNA replication introduces a mismatch in a double-stranded DNA,the methyl-directed repair system:

Accepted Answer

A)  cannot distinguish the template strand from the newly replicated strand.
B)  changes both the template strand and the newly replicated strand.
C)  corrects the DNA strand that is methylated.
D)  corrects the mismatch by changing the newly replicated strand.
E)  corrects the mismatch by changing the template strand.F) C) and E)
G) B) and C)

Question 15

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen) is similar to that of the  β\betaβ -subunit of bacterial DNA polymerase III in that it:

Accepted Answer

A)  facilitates replication of telomeres.
B)  forms a circular sliding clamp to increase the processivity of replication.
C)  has a 3'  →\rightarrow→   5' proofreading activity.
D)  increases the speed but not the processivity of the replication complex.
E)  participates in DNA repair. F) A) and E)
G) A) and D)

Question 16

Nucleotide polymerization appears to be a thermodynamically balanced reaction (because one phosphodiester bond is broken and one is formed).Nevertheless,the reaction proceeds efficiently both in a test tube and in the cell.Explain.

Accepted Answer

Base-stacking and base-pairing interacti...

Question 17

Describe briefly how equilibrium density gradient centrifugation was used to demonstrate that DNA replication in E.coli is semiconservative.

Accepted Answer

Equilibrium density gradient centrifugat...

Question 18

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.coli?

Accepted Answer

A)  DNA glycosylase
B)  DNA helicase II
C)  DNA ligase
D)  DNA polymerase III
E)  Exonuclease IF) A) and E)
G) C) and D)

Question 19

DNA replication in E.coli begins at a site in the DNA called the (a)___________.At the replication fork the (b)___________ strand is synthesized continuously while the (c)_________ strand is synthesized discontinuously.On the strand synthesized discontinuously,the short pieces are called (d)____________ fragments.An RNA primer for each of the fragments is synthesized by an enzyme called (e)__________,and this RNA primer is removed after the fragment is synthesized by the enzyme (f)___________,using its (g)_____________ activity.The nicks left behind in this process are sealed by the enzyme (h)_____________.

Accepted Answer

(a)origin;
(b)leading;
(c)la...

Question 20

Which of the following is false about transposition of DNA?

Accepted Answer

A)  The diversity of immunoglobins is in part due to DNA recombination by transposition.
B)  Transposition occurs in both prokaryotes and eukaryotes.
C)  Enzymes are not required for transposition.
D)  The first step of transposition can be single- or double-stranded DNA cleavage.
E)  Transposition can lead to simple movement of a DNA region or duplication of that region in a new location.F) All of the above
G) B) and E)

Exam 25: Dna Metabolism

In homologous recombination in E.coli,the protein that moves along a double-stranded DNA,unwinding the strands ahead of it and degrading them,is:

Correct Answer
verified

When bacterial DNA replication introduces a mismatch in a double-stranded DNA,the methyl-directed repair system:

Correct Answer
verified

Which of the following is false about transposition of DNA?

Correct Answer
verified

Correct Answer
verified
(a)origin;
(b)leading;
(c)la...
View Answer

Outline the key steps that occur during meiosis in animal germ-line cells.

Correct Answer
verified
The chromosomes of a diploid cell are du...
View Answer

What is an Okazaki fragment? What enzyme(s)is (are)required for its formation in E.coli?

Correct Answer
verified
An Okazaki fragment is an intermediate i...
View Answer

Nucleotide polymerization appears to be a thermodynamically balanced reaction (because one phosphodiester bond is broken and one is formed).Nevertheless,the reaction proceeds efficiently both in a test tube and in the cell.Explain.

Correct Answer
verified
Base-stacking and base-pairing interacti...
View Answer

In contrast to bacteria,eukaryotic chromosomes need multiple DNA replication origins because:

Correct Answer
verified

List two proteins or enzymes,other than DNA polymerase III,that are found at the replication fork in E.coli.Describe each of their functions with no more than one sentence.

Correct Answer
verified
The proteins are listed in Table 25-4.Th...
View Answer

Which mechanism is used to repair a chemically modified base in DNA?

Correct Answer
verified

Correct Answer
verified
In the cell,initiation of DNA chains occ...
View Answer

Explain the role of DNA glycosylases in DNA repair.

Correct Answer
verified
When spontaneous deamination converts cy...
View Answer

The Ames test is used to:

Correct Answer
verified

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.coli?

Correct Answer
verified

The ABC excinuclease is essential in:

Correct Answer
verified

Explain how inheriting mutations in genes encoding DNA repair enzymes could lead to increased cancer risk.

Correct Answer
verified
Mutations in DNA repair genes ...
View Answer

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen) is similar to that of the $\beta$ -subunit of bacterial DNA polymerase III in that it:

Correct Answer
verified

What distinguishes the two mechanistic pathways for transposition in bacteria,and what is a cointegrate?

Correct Answer
verified
Direct transposition moves the transposo...
View Answer

In the bacterial cell,what are catenated chromosomes,when do they arise,and how does the cell resolve the problem posed by their structure?

Correct Answer
verified
Catenanes are topologically interlinked ...
View Answer

Describe briefly how equilibrium density gradient centrifugation was used to demonstrate that DNA replication in E.coli is semiconservative.

Correct Answer
verified
Equilibrium density gradient centrifugat...
View Answer

Exam 25: Dna Metabolism

In homologous recombination in E.coli,the protein that moves along a double-stranded DNA,unwinding the strands ahead of it and degrading them,is:

Correct AnswerverifiedShow Answer

When bacterial DNA replication introduces a mismatch in a double-stranded DNA,the methyl-directed repair system:

Correct AnswerverifiedShow Answer

Which of the following is false about transposition of DNA?

Correct AnswerverifiedShow Answer

Correct Answerverified(a)origin; (b)leading; (c)la...View AnswerShow Answer

Outline the key steps that occur during meiosis in animal germ-line cells.

Correct AnswerverifiedThe chromosomes of a diploid cell are du...View AnswerShow Answer

What is an Okazaki fragment? What enzyme(s)is (are)required for its formation in E.coli?

Correct AnswerverifiedAn Okazaki fragment is an intermediate i...View AnswerShow Answer

Nucleotide polymerization appears to be a thermodynamically balanced reaction (because one phosphodiester bond is broken and one is formed).Nevertheless,the reaction proceeds efficiently both in a test tube and in the cell.Explain.

Correct AnswerverifiedBase-stacking and base-pairing interacti...View AnswerShow Answer

In contrast to bacteria,eukaryotic chromosomes need multiple DNA replication origins because:

Correct AnswerverifiedShow Answer

List two proteins or enzymes,other than DNA polymerase III,that are found at the replication fork in E.coli.Describe each of their functions with no more than one sentence.

Correct AnswerverifiedThe proteins are listed in Table 25-4.Th...View AnswerShow Answer

Which mechanism is used to repair a chemically modified base in DNA?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedIn the cell,initiation of DNA chains occ...View AnswerShow Answer

Explain the role of DNA glycosylases in DNA repair.

Correct AnswerverifiedWhen spontaneous deamination converts cy...View AnswerShow Answer

The Ames test is used to:

Correct AnswerverifiedShow Answer

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.coli?

Correct AnswerverifiedShow Answer

The ABC excinuclease is essential in:

Correct AnswerverifiedShow Answer

Explain how inheriting mutations in genes encoding DNA repair enzymes could lead to increased cancer risk.

Correct AnswerverifiedMutations in DNA repair genes ...View AnswerShow Answer

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen) is similar to that of the β\betaβ -subunit of bacterial DNA polymerase III in that it:

Correct AnswerverifiedShow Answer

What distinguishes the two mechanistic pathways for transposition in bacteria,and what is a cointegrate?

Correct AnswerverifiedDirect transposition moves the transposo...View AnswerShow Answer

In the bacterial cell,what are catenated chromosomes,when do they arise,and how does the cell resolve the problem posed by their structure?

Correct AnswerverifiedCatenanes are topologically interlinked ...View AnswerShow Answer

Describe briefly how equilibrium density gradient centrifugation was used to demonstrate that DNA replication in E.coli is semiconservative.

Correct AnswerverifiedEquilibrium density gradient centrifugat...View AnswerShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
(a)origin;
(b)leading;
(c)la...
View Answer

Correct Answer
verified
The chromosomes of a diploid cell are du...
View Answer

Correct Answer
verified
An Okazaki fragment is an intermediate i...
View Answer

Correct Answer
verified
Base-stacking and base-pairing interacti...
View Answer

Correct Answer
verified

Correct Answer
verified
The proteins are listed in Table 25-4.Th...
View Answer

Correct Answer
verified

Correct Answer
verified
In the cell,initiation of DNA chains occ...
View Answer

Correct Answer
verified
When spontaneous deamination converts cy...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Mutations in DNA repair genes ...
View Answer

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen) is similar to that of the $\beta$ -subunit of bacterial DNA polymerase III in that it:

Correct Answer
verified

Correct Answer
verified
Direct transposition moves the transposo...
View Answer

Correct Answer
verified
Catenanes are topologically interlinked ...
View Answer

Correct Answer
verified
Equilibrium density gradient centrifugat...
View Answer