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You take a sample of bacteria with DNA that contains only 14N and allow them to replicate in a medium that contains only 15N.After 3 rounds of replication,what percent of the DNA molecules will contain one strand with only 14N and one strand with only 15N? Enter your answer as a whole number without the percent sign.For example,5% would be entered as 5 and 37% would be entered as 37.

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If we think of the DNA double helix as a twisted ladder,what makes up the rungs or steps of the ladder?


A) phosphate groups only
B) alternating phosphate groups and sugars
C) sugars only
D) purines and pyrimidines
E) phosphate groups and bases

F) B) and D)
G) A) and D)

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Nucleotides have a phosphate group attached at the ________ carbon atom of the sugar.


A) 2'
B) 3'
C) 5'
D) 1'

E) B) and D)
F) B) and C)

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Who originally discovered the process of bacterial transformation?


A) Watson and Crick
B) Chargaff
C) Hershey and Chase
D) Griffith
E) Meselson and Stahl

F) C) and D)
G) A) and C)

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Which is not a component of nucleic acids?


A) organic nitrogenous base
B) pentose sugar
C) phosphate
D) sulfur

E) B) and C)
F) None of the above

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An organism has been found to contain a defective form of photolyase.What function might be impaired in this organism?


A) Lengthening of the tips of chromosomes
B) Repair of DNA damage caused by UV light
C) Stabilization of single-stranded DNA during DNA replication
D) Recognition of damaged DNA by the UvrABC complex

E) A) and D)
F) None of the above

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After attaching to a bacterial cell,a bacteriophage typically


A) injects protein into the cell.
B) extracts protein from the cell.
C) injects DNA into the cell.
D) extracts DNA from the cell.
E) transforms the cell into a virulent strain.

F) A) and E)
G) A) and D)

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The double helix model of DNA structure was proposed by


A) Watson and Crick.
B) Griffith.
C) Avery.
D) Franklin.
E) Chargaff.

F) A) and E)
G) C) and D)

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The chemical bond connecting one nucleotide with the next along one strand of a DNA molecule is called a


A) glycosidic bond.
B) hydrogen bond.
C) phosphate bond.
D) phosphodiester bond.
E) peptide bond.

F) B) and D)
G) B) and C)

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Replication of DNA is


A) conservative.
B) redundant.
C) dispersive.
D) semiconservative.
E) semidispersive.

F) None of the above
G) D) and E)

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DNA replication always proceeds by adding new bases to the ________ end of an existing strand.


A) 1'
B) 2'
C) 3'
D) 4'
E) 5'

F) All of the above
G) None of the above

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Why does DNA pol I carry the number one?


A) It was the first polymerase isolated from E.coli.
B) It is the first polymerase to be activated during DNA replication.
C) It is the only polymerase that has both 3' to 5' and 5' to 3' exonuclease activity.
D) It is the smallest polymerase.

E) B) and C)
F) None of the above

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During DNA replication,each new strand begins with a short


A) amino acid primer.
B) lipid primer.
C) hydrophilic primer.
D) DNA primer.
E) RNA primer.

F) C) and E)
G) C) and D)

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Which enzyme adds new nucleotides to the end of a growing strand?


A) ligase
B) polymerase
C) gyrase
D) helicase
E) endonuclease

F) A) and C)
G) C) and D)

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Avery,MacLeod,and McCarty's experiments revealed that the transforming principle had all of the following properties except


A) its activity was destroyed by treatment with proteases.
B) its activity was unaffected by RNA-digesting enzymes.
C) its activity was unaffected by lipid extraction.
D) its activity was destroyed by treatment with DNA endonucleases.

E) All of the above
F) None of the above

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Genetic analysis indicates that an unknown organism contains a gene that codes for a defective form of telomerase.Based on this information alone,you can conclude that this organism


A) is prokaryotic.
B) is eukaryotic.
C) has unusually long telomeres.
D) has an increased risk of developing cancer.

E) All of the above
F) C) and D)

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Suppose a new species of bacterium is discovered.It contains a form of DNA pol III that can add new nucleotides to either the 5' end or the 3' end of an existing strand.All other properties of the enzyme remain unchanged.How would DNA replication in these bacteria differ from normal replication?


A) Both new strands could be synthesized continuously like the leading strand.
B) The same polymerase molecule could synthesize both strands at the same time.
C) Helicase would no longer be required for replication.
D) DNA gyrase would no longer be required for replication.

E) B) and C)
F) A) and B)

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Which of the following statements about DNA replication is false?


A) The two strands are separated.
B) Each existing strand is used as a template for making a new strand.
C) Synthesis of both new strands is in the 5' to 3' direction.
D) The newly synthesized DNA is packaged into one nucleus,and the original DNA is packaged into another nucleus.

E) A) and B)
F) A) and C)

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Who demonstrated that phage genetic material is DNA and not protein?


A) Hershey and Chase
B) Chargaff
C) Franklin
D) Watson and Crick
E) Avery,MacLeod,and McCarty

F) A) and D)
G) None of the above

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The synthesis of a growing strand of DNA is carried out by adding nucleotides to the ________ end of an existing strand.


A) 2'
B) 3'
C) 5'
D) 1'

E) A) and C)
F) A) and D)

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