Deck 10: Biosynthesis of Nucleic Acids: Replication

Question 1

Which of the following is not a function of DNA Polymerase III?

A) Polymerization.
B) Ligating the final products.
C) Proofreading.
D) Clamping on to the template.
E) All of these.

Answer 1

B

Question 2

The duplication process of DNA is called

A) replication.
B) transcription.
C) translation.
D) nucleation.

Answer 2

A

Question 3

The flow of genetic information is RNA DNA in

A) all organisms.
B) all prokaryotes.
C) retroviruses.
D) no known organisms.

Answer 3

C

Question 4

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

A) the DNA produced has two newly formed strands (no change in the original DNA)
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 5

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?

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 6

Which of the following best describes the process of DNA replication in a prokaryote?

A) Replication begins at a unique site and proceeds in one direction all the way around a typically circular chromosome.
B) Replication begins at a unique site and proceeds in two directions, meeting about halfway around a typically circular chromosome.
C) Replication begins at multiple sites, spreading outward until the entire typically circular chromosome is replicated.
D) Replication begins at multiple sites, spreading outward until the entire typically linear chromosome is replicated.

Question 7

The direction of synthesis of a DNA strand is

A) from the 5' end to the 3' end on both strands.
B) from the 3' end to the 5' end on both strands.
C) from the 5' end to the 3' end on one strand and from the 3' end to the 5' end on the other strand.
D) none of the above.

Question 8

The following enzyme is responsible for the bulk of DNA synthesis during replication.

A) DNA Polymerase I
B) DNA Polymerase II
C) DNA Polymerase III
D) DNA Polymerases IV
E) All four can make lots of DNA rapidly.

Question 9

What is the requirement for a template strand in DNA replication?

A) It serves as a guide in determining the next nucleotide to be added according to the Watson-Crick base pairing scheme.
B) It serves as the start point for the new DNA strand.
C) It allows the DNA polymerase to move along it easily.
D) It is a substrate for the 3'-5' exonuclease activity.

Question 10

The famous Meselson and Stahl experiment showed:

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 11

Semiconservative replication of DNA was established experimentally by

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

Question 12

The process by which an mRNA base sequence directs the amino acid sequence of a protein is called

A) replication.
B) transcription.
C) translation.
D) nucleation.

Question 13

In the original Central Dogma of biology,the ordinary flow of genetic information is:

A) DNA RNA Protein
B) RNA DNA Protein
C) Protein RNA DNA
D) DNA Protein RNA.
E) None of these

Question 14

Semiconservative replication implies that

A) each of the new double stranded DNA molecules contains one of the original intact strands and one completely new strand.
B) one of the new double stranded DNA molecules contains both of the original strands, while the other contains two new strands.
C) each of the new double stranded DNA molecules contains strands that are composed of segments of original and newly synthesized material.
D) None of these.

Question 15

All the following describe the general mechanism of DNA synthesis,except:

A) From the perspective of the DNA template strands, one strand is made 5' 3' while the other strand is made 3' 5'.
B) The strands become separated during synthesis.
C) Synthesis occurs in both directions from the starting site of synthesis.
D) Synthesis of DNA is a very accurate process.
E) All of these are correct.

Question 16

The universal features of DNA replication include all the following,except:

A)Release of PPi from a nucleoside triphosphate.
B)Synthesis from the 5' end to the 3' end.
C)Base pairing of A to T and G to C.
D)Use of a primer.
E)All of these describe DNA synthesis.

Question 17

The production of RNA on a DNA template is called

A) replication.
B) transcription.
C) translation.
D) nucleation.

Question 18

How do origins of replication differ in eukaryotes and prokaryotes?

A) Eukaryotes have several origins, while prokaryotes typically have one.
B) Prokaryotes have several origins, while eukaryotes typically have one.
C) Only prokaryotes have origins of replication.
D) None of these.

Question 19

An important process in the synthesis of new DNA is

A) proofreading and repair.
B) unwinding of the double helix.
C) protection of single-stranded regions from nuclease action.
D) all of these

Question 20

DNA replication is a challenging process because:

A) DNA strands must be separated
B) New DNA is always synthesized from the 5' 3' direction but the two template strands run in opposite directions
C) The cell must guard against replication errors
D) All of these

Question 21

Which of the following activities does

A)5' 3' polymerase
B)5' 3' exonuclease
C)3' 5' exonuclease
D)E.coli DNA polymerase III has ALL of the above activities.

Question 22

The mechanism for all template-directed synthesis of any type of nucleic acid involves the following:

A) Nucleophilic attack of a 3' hydroxyl toward a nucleoside triphosphate, releasing PP_i.
B) Nucleophilic attack of a 5' hydroxyl toward a nucleoside triphosphate, releasing PP_i.
C) Nucleophilic attack of a 3' hydroxyl toward a nucleoside triphosphate, releasing P_i.
D) Nucleophilic attack of a 5' hydroxyl toward a nucleoside triphosphate, releasing P_i.
E) More than one of these would work, since the mechanism is not universal.

Question 23

The primer for in vivo DNA replication is:

A) The 3' hydroxyl of the preceding Okazaki fragment.
B) A short piece of RNA.
C) A nick made in the DNA template.
D) A primer is not always required for DNA replication.
E) All of these are true.

Question 24

In prokaryotic replication,all DNA polymerases are capable of all of the following tasks except:

A) Reading a template strand and putting the complementary base in the correct position
B) Polymerizing DNA in the 5' to 3' direction
C) Excising DNA in the 3' to 5' direction
D) Excising DNA in the 5' to 3' direction
E) All of these are capabilities of all DNA polymerases

Question 25

In Escherichia coli,the enzyme principally responsible for the synthesis of new DNA strands is

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

Question 26

In E.coli,

A) the leading strand is synthesized in one piece while the lagging strand is synthesized discontinuously.
B) the leading strand is synthesized discontinuously while the lagging strand is synthesized in one piece.
C) both the leading and lagging strands are synthesized in one piece.
D) both the leading and lagging strands are synthesized discontinuously.

Question 27

In the synthesis of DNA in Escherichia coli

A) a single-strand nick in the template DNA gives rise to a swivel point just in advance of the replication fork
B) Mn²⁺ is required
C) all enzymes involved are single polypeptide chains
D) neither the template DNA nor the daughter DNA molecules exhibit supercoiling

Question 28

The energetic driving force for nucleic acid synthesis is

A) removal of pyrophosphate from the incoming nucleotide.
B) removal of pyrophosphate from the growing strand.
C) removal of inorganic phosphate from the incoming nucleotide.
D) removal of inorganic phosphate from the growing strand.

Question 29

Which of the following is not a function of DNA polymerase I from E.coli?

A) adding nucleotides to the primer strand
B) 3' 5' exonuclease activity
C) 5' 3' exonuclease activity
D) proofreading

Question 30

In order to replicate both strands,E.coli

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 31

DNA polymerase III from E.coli

A) is a large, multisubunit protein
B) has a sliding clamp portion that anchors it to DNA
C) has a polymerization site separate from the DNA binding site
D) all of these

Question 32

Exhibit 10A Consider the following diagrams showing a replication fork moving from left to right.The thick lines represent the template/parental strands.The 5' and 3' represent the ends of those template/parental strands.
Refer to Exhibit 10A.Which diagram correctly depicts the orientation of the lagging and leading strands on the parentals?

A) The top
B) The bottom
C) Neither is fully accurate.
D) Either would be accurate dependent on the organism being studied.

Question 33

AZT,used in treating AIDS,is an effective inhibitor of nucleic acid synthesis because:

A) It has a nitrogen group instead of a 3' OH.
B) It is a 2', 3' dideoxy compound.
C) It doesn't form good base pairs.
D) It inhibits RNA Polymerase needed to make RNA for new HIV virus particles.
E) More than one of these is correct.

Question 34

Exhibit 10A Consider the following diagrams showing a replication fork moving from left to right.The thick lines represent the template/parental strands.The 5' and 3' represent the ends of those template/parental strands.
Refer to Exhibit 10A.Which Okazaki fragment was synthesized earliest?

A) A
B) B
C) C
D) D

Question 35

Which of the following characteristics is not associated with

A) it synthesizes the RNA primer in DNA replication
B) it synthesizes a primer with a free 3'-OH end
C) it is essential for DNA replication
D) it is essential for RNA replication
E) coli primase?

Question 36

E.coli replication on the lagging strand

A) is carried out by DNA polymerase I
B) is initially synthesized as Okazaki fragments
C) is synthesized continuously
D) has this DNA strand synthesized in a 3' 5' direction

Question 37

Why is thymine used in DNA rather than uracil?

A) Thymine is more hydrophobic, so it stacks better in the helix.
B) If cytosine is deaminated, it forms uracil, which can be easily distinguished from thymine.
C) Thymine is not capable of wobbling, so it pairs more accurately than uracil.
D) All of these are correct.

Question 38

Okazaki fragments are

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 39

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

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 40

What is the need for a primer strand in DNA replication?

A) it ensures the fidelity of the newly synthesized DNA strand
B) the DNA polymerases require a preexisting strand with a nucleotide having a 3'-OH
C) the DNA polymerases require a preexisting strand with a nucleotide having a 5'-OH
D) it ensures the integrity of the new DNA

Question 41

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

Question 42

Which of the following statements is true about the so-called "MUT" (for "mutation") repair mechanisms?

A) Depend on the methylation of old strands of DNA to determine which strand to repair.
B) Often remove hundreds or even thousands of bases during the repair process.
C) Can only repair mismatches that occur during the normal replication process.
D) All of these are true.

Question 43

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

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

Question 44

Which of these proteins is used less for leading strand replication than for lagging strand replication?

A) DNA polymerase
B) DNA-binding protein
C) DNA ligase
D) DNA gyrase

Question 45

Repair of DNA is usually carried out by

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 46

Which of the activities of DNA Polymerase I is most important in its role of proofreading?

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 proofreading.

Question 47

Which of the following enzymes is used to create AP sites?

A) primase
B) helicase
C) ligase
D) glycosylase

Question 48

Which of the following repair mechanisms would most likely be used to repair a G in DNA damaged by oxidation?

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

Question 49

Which of the following mechanisms allow repair enzymes to distinguish incorrect bases in DNA?

A) The newly synthesized strand of DNA lacks methylated bases and other modifications.
B) Deamination of A and C lead to improper bases for DNA.
C) Thymine dimers and other cross links kink the DNA and are easy to find.
D) All of these mechanisms allow repair enzymes to distinguish which base is incorrect.

Question 50

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

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 51

The enzyme that attaches the Okazaki fragments together is called

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

Question 52

DNA repair mechanisms are essentially the same whether the DNA has minor damage or major damage.

Question 53

Which of the following is not required for optimal DNA replication?

A) Primase
B) DNA Polymerase II.
C) Single strand binding proteins.
D) Gyrase
E) All of these are necessary.

Question 54

The proofreading of DNA is especially good because "the identity of each base pair is checked before the enzyme moves on to the next base pair."

Question 55

Which is most likely to have a high processivity?

A) a DNA polymerase that is primarily a repair enzyme
B) a primase
C) a DNA ligase
D) a DNA polymerase that is a main polymerizing enzyme

Question 56

Since DNA Polymerase II has endonuclease activity,it is able to proofread its product when it is used in DNA repair.

Question 57

Which of the following is not an activity of DNA Polymerase I?

A) Polymerase activity.
B) Ability to nick intact double stranded DNA.
C) 5' 3' exonuclease.
D) 3' 5' exonuclease.
E) All of these are present in DNA Pol I.

Question 58

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

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

Question 59

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

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 60

Single strand binding proteins are important for this activity:

A) Prevent single-stranded DNA from rewinding.
B) Protect single-stranded DNA from enzymatic degradation.
C) Prevent double helical DNA from unwinding.
D) Prevent double helical DNA from becoming a triple helix.
E) Prevent single-stranded DNA from rewinding and protect it from degradation.

Question 61

How do the Okazaki fragments of eukaryotes and prokaryotes compare?

A) The Okazaki fragments are much longer in eukaryotes than in prokaryotes.
B) The Okazaki fragments are much shorter in eukaryotes than in prokaryotes.
C) The Okazaki fragments of eukaryotes are on the leading strand, rather than the lagging strand.
D) There is little to no difference between the Okazaki fragments of eukaryotes and prokaryotes.

Question 62

Linear eukaryotic DNA molecules

A) have many origins of synthesis, while circular bacterial DNA usually have only one.
B) have only one origin of synthesis, while circular bacterial DNA usually have many.
C) are synthesized fully conservatively, while circular bacterial DNA is synthesized semi-conservatively.
D) are synthesized dispersively, while circular bacterial DNA is synthesized semi-conservatively.

Question 63

The enzyme telomerase uses mechanisms that involve:

A) Repeating sequences at the telomeres.
B) Having RNA oligonucleotides to act as templates as part of the enzyme.
C) Allowing the end of the chromosome to get a little shorter each time a cell divides.
D) Both repeating sequences at the end of chromosomes and RNA oligonucleotides to act as templates as part of the enzyme.
E) All of these.

Question 64

Telomerase activity may decline with old age and this could explain why cells lose their ability to divide after many replications.

Question 65

Telomerase activity in cancer cells may explain their longevity.

Question 66

Eukaryotes need more types of DNA polymerases than bacteria because

A) the DNA-containing organelles have their own DNA polymerases.
B) they have linear DNA , which is harder to replicate than circular DNA.
C) because they have more kinds of bases in their DNA than the four used by prokaryotes.
D) That's not true; eukaryotes do not have more types of DNA polymerases.

Question 67

Which of the following is a characteristic of eukaryotic,but not prokaryotic,DNA replication?

A) Topoisomerases are required.
B) A primer is needed on the lagging strand only.
C) Histone biosynthesis must take place.
D) There is only one origin of replication.

Question 68

Both eukaryotes and prokaryotes use a dimeric DNA Polymerase for DNA replication.

Question 69

Recombination:

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 70

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

Question 71

Which of the following describes a difference between DNA polymerases in eukaryotes and bacteria?

A) Some eukaryotic polymerases include a primase.
B) All the eukaryotic enzymes are polymeric.
C) Eukaryotes require a special enzyme to remove the RNA primer.
D) Some eukaryotic polymerases include a primase and all are polymeric.
E) All of these are correct.

Question 72

One of the most important ways in which eukaryotic DNA differs from that of prokaryotes is

A) prokaryotic DNA is complexed to proteins whereas eukaryotic DNA is not
B) eukaryotic DNA is complexed to proteins whereas prokaryotic DNA is not
C) DNA synthesis in eukaryotes takes place in the opposite direction from that in prokaryotes
D) there is no requirement for a primer in the synthesis of eukaryotic DNA

Question 73

Which of the following play a role in DNA replication in eukaryotes?

A) cyclin-dependent kinases
B) origin recognition complex
C) replication licensing factors
D) all of these

Question 74

The mechanism of breakage and reunion of DNA strands during recombination was proposed by:

A) Messelson and Stahl
B) Messelson and Weigle
C) Robin Holliday
D) Francis Crick

Question 75

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.

Question 76

The DNA polymerases in eukaryotes have similar functions to those found in bacteria,but they are not identical.

Question 77

Replication of eukaryotic DNA

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

Question 78

In eukaryotic replication,the RNA primers are degraded by:

A) the 5' to 3' exonuclease activity of pol ä
B) DNA ligase
C) Helicase
D) FEN-1 and RNase H1

Question 79

Eukaryotic DNA polymerases differ from those of prokaryotes in that

A) they do not require a primer
B) they do not always have exonuclease activity
C) there is no equivalent to the sliding clamp in prokaryotic replication
D) they produce longer Okazaki fragments