Deck 3: DNA Replication

Question 1

Where does the initiator protein bind DNA at the start of replication?

A)At a replication fork
B)At an origin of replication
C)At any AT-rich region
D)At a promoter region
E)At a start codon

Answer 1

B

Question 2

As helicase unwinds the DNA molecule,what keeps the strands apart?

A)DNA polymerase
B)Reverse transcriptase
C)Replication fork
D)Single-strand binding proteins
E)Okazaki fragments

Answer 2

D

Question 3

In E.coli,replication begins at which chromosome site?

A)The replication fork
B)ter
C)oriC
D)TBP
E)All of these

Answer 3

C

Question 4

In Meselson and Stahl's experiment,what kind of DNA molecules would be found after four replication cycles?

A)Only heavy DNA (¹⁵N-¹⁵N)
B)Only intermediate DNA (¹⁵N-¹⁴N)
C)Only light DNA (¹⁴N-¹⁴N)
D)Both heavy (¹⁵N-¹⁵N)and light DNA (¹⁴N-¹⁴N)
E)Both heavy (¹⁵N-¹⁵N)and intermediate DNA (¹⁵N-¹⁴N)

Question 5

Which of the following did Kornberg use to detect DNA synthesis?

A)Radioactively labeled E.coli cells
B)Fluorescently labeled E.coli cells
C)Radioactively labeled deoxynucleotide triphosphates
D)Fluorescently labeled deoxynucleotide triphosphates
E)Nonlabeled deoxynucleotide triphosphates

Question 6

During replication,the direction of synthesis of new DNA from the leading and lagging strands is

A)5' to 3' only.
B)3' to 5' only.
C)from left to right only.
D)both 5' to 3' and 3' to 5'.
E)different,depending on whether the cell is prokaryotic or eukaryotic.

Question 7

Which kind of enzyme prevents DNA from tangling up by introducing negative supercoils as the replication fork migrates during replication?

A)Helicase
B)Ligase
C)DNA polymerase I
D)DNA polymerase III
E)Topoisomerase

Question 8

After removal of the RNA primers and replacement with DNA nucleotides,the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme?

A)DNA primase
B)SSB protein
C)RNA polymerase
D)DNA ligase
E)DNA helicase

Question 9

DNA replication is always

A)discontinuous.
B)bidirectional.
C)conservative.
D)semiconservative.
E)dispersive.

Question 10

Rolling circle replication of DNA is characterized by the absence of

A)the DNA polymerase.
B)a nick in the DNA template.
C)the RNA primers.
D)the replication bubble.
E)the Okazaki fragments.

Question 11

After a region of DNA has been replicated,________ removes the RNA primers.

A)DNA polymerase I
B)DNA polymerase III
C)DNA helicase
D)RNA primase
E)DNA ligase

Question 12

How many replication forks are produced when DNA denatures at an origin?

A)0
B)1
C)2
D)3
E)The number varies

Question 13

The enzymatic activity of a telomerase is best described as a

A)polymerase.
B)ligase.
C)topoisomerase.
D)reverse transcriptase.
E)exonuclease.

Question 14

The two most basic steps of DNA replication are

A)primase causes primer to bind the template and ligase copies the template.
B)helicase unwinds the template and DNA polymerase binds the template.
C)leading strand is copied first and lagging strand is copied second.
D)the new strand is denatured and a template is synthesized.
E)the template is denatured and a new strand is synthesized.

Question 15

Which of the following are necessary for DNA replication in vitro?

A)RNA,helicase,primers,DNA polymerase
B)Okazaki fragments,helicase,DNA polymerase
C)Template DNA,DNA polymerase,four dNTPs,primers,magnesium ions
D)Template DNA,four dNTPs,magnesium ions
E)DNA can't replicate in vitro

Question 16

Which enzyme replaces RNA primers with DNA after elongation?

A)DNA polymerase I
B)DNA polymerase III
C)RNA polymerase
D)RNA primase
E)DNA ligase

Question 17

Which enzyme elongates the new DNA strand starting at an RNA primer?

A)DNA polymerase I
B)DNA polymerase III
C)RNA primase
D)DNA ligase
E)RNA polymerase

Question 18

What is a replication bubble?

A)A complex of replication enzymes on the DNA template strand
B)A DNA sequence that initiates replication
C)A tangle of denatured DNA strands near the replication fork
D)A locally denatured segment of DNA where replication originates
E)A localized site in the nucleus where chromosomes are replicating

Question 19

The base-pairing error rate remains low during replication because

A)DNA repair mechanisms can fix the mispaired bases.
B)bases that are mispaired can excise themselves.
C)UV light radiation corrects any base mispairs.
D)mispaired bases cause a cell to die before replication is complete.
E)None of these; base-pairing errors are not possible

Question 20

The diploid set of chromosomes in Drosophila embryos replicates six times faster than the single E.coli chromosome,even though there is about 100 times more DNA in Drosophila than in E.coli and the rate of movement of the replication fork in Drosophila is much slower.How is this so?

Question 21

A cross is made between yeast cells with different alleles for a set of linked genes: pr^+q × p^+rq+.The resulting tetrads show a 3:1 ratio for r⁺ to r instead of the expected 2:2 ratio.Can you explain how this could have occurred?

Question 22

Why is an AT-rich sequence characteristic of DNA replicators in all organisms?

Question 23

What are some key differences in replication between E.coli DNA and λ phage DNA?

Question 24

In eukaryotes,DNA replication begins at a single origin of replication on each chromosome.

Question 25

DNA polymerase III is very inaccurate at matching bases during replication,with errors in one out of every 100 base pairs.

Question 26

A new nucleotide is added to a growing strand of DNA at the 3' end.

Question 27

Why is DNA replication referred to as semiconservative?

Question 28

In eukaryotic cells,histone proteins are actively synthesized during the S phase of the cell cycle.

Question 29

What are the differences in replication between leading and lagging strands in terms of continuity and directionality in relation to the replication fork?

Question 30

Topoisomerase and SSB proteins are important components of the replication process in prokaryotes,but they are not found in eukaryotes.

Question 31

Describe the method devised by Arthur Kornberg which first successfully achieved DNA synthesis in vitro,including its components and their uses.

Question 32

At the growing end of a DNA chain,DNA polymerase catalyzes the formation of a disulfide bond between the 3'-OH group of the deoxyribose on the last nucleotide and the 5'-phosphate of the dNTP precursor.

Question 33

What experiment demonstrated that the 5'-to-3' exonuclease activity of DNA polymerase I was essential for cell viability?

Question 34

DNA primase is an RNA polymerase.

Question 35

Mg²⁺ ions are required for optimal DNA polymerase activity.

Question 36

Okazaki fragments are made from the lagging strand of the DNA double helix.

Question 37

Which enzyme activity is associated with the proofreading mechanism of DNA polymerase I?

A)5'-to-3' exonuclease activity
B)3'-to-5' exonuclease activity
C)5'-to-3' polymerase activity
D)Both A and B
E)All of these

Question 38

Only the leading strand of a DNA molecule serves as a template during replication.

Question 39

What are the key replication enzymes at the replisome,and how is DNA replication on both leading and lagging strands made efficient through the conformation of the DNA at the replisome in prokaryotes?

Question 40

When the RNA primers are removed from the 5' ends of eukaryotic chromosomes after replication,DNA polymerase is unable to fill in the gaps.What prevents the chromosomes from getting shorter and shorter with each round of replication?

Question 41

How were the sequences that compose the replication origins in yeast discovered?

Question 42

Why do tumor cells in mammals have telomerase activity?

Question 43

How will DNA replication be affected if DNA polymerase I has a mutation that inactivates 5'-to-3' exonuclease activity?

Question 44

How did Meselson and Stahl rule out the conservative model of DNA replication using equilibrium density gradient centrifugation?

Question 45

How do the DNA polymerase repair mechanisms work?