Biosynthesis of Nucleic Acids: Replication

Question 1

The duplication process of DNA is called
a. replication.
b. transcription.
c. translation.
d. nucleation.

Answer 1

a

Question 2

The production of RNA on a DNA template is called
a. replication.
b. transcription.
c. translation.
d. nucleation.

Answer 2

b

Question 3

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.

Answer 3

c

Question 4

The flow of genetic information is RNA → DNA in
a. all organisms.
b. all prokaryotes.
c. retroviruses.
d. no known organisms.

Answer 4

c

Question 5

Which of the following is NOT an observed event in the flow of genetic information?
a. DNA –> RNA
b. RNA –> DNA
c. RNA –> RNA
d. DNA –> DNA
e. RNA –> Protein
f. Protein –> RNA
g. All of the choices ARE observed

Answer 5

f

Question 6

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.

Answer 6

a

Question 7

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

Answer 7

a

Question 8

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.

Answer 8

a

Question 9

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.

Answer 9

a

Question 10

If replication were conservative instead of semi-conservative, the famous Meselson and Stahl experiment would have
shown which of the following results after the first round of replication?
a. All of the double helices would have been heavy chains
b. All of the double helices would have been light chains
c. Half of the double helices would have been all heavy chains and the other half would have been all light
chains
d. All of the double helices would have been a combination of a heavy strand and a light strand

Answer 10

c

Question 11

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.

Answer 11

e

Question 12

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

Answer 12

d

Question 13

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.

Answer 13

a

Question 14

Semiconservative replication of DNA was established experimentally by
a. gel electrophoresis.
b. ultraviolet spectroscopy.
c. column chromatography.
d. density-gradient centrifugation.

Answer 14

d

Question 15

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.

Answer 15

c

Question 16

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.

Answer 16

a

Question 17

DNA is synthesized from the 3’ end to the 5’ end in which of the following processes?
a. Replication of DNA
b. Replication of RNA
c. Transcription of RNA from DNA
d. none of these

Answer 17

d

Question 18

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

Answer 18

d

Question 19

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.

Answer 19

b

Question 20

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

Answer 20

b

Question 21

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. None of these are functions of DNA Polymerase III

Answer 21

b

Question 22

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.

Answer 22

c

Question 23

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.

Answer 23

e

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

Answer 24

d

Question 25

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.

Answer 25

a

Question 26

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.

Answer 26

e

Question 27

Which of the following activities does E. coli DNA polymerase III lack? a. 5' → 3' polymerase b. 5' → 3' exonuclease c. 3' → 5' exonuclease d. E. coli DNA polymerase III has ALL of the above activities.

Answer 27

b

Question 28

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.

Answer 28

b

Question 29

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.

Answer 29

a

Question 30

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

Answer 30

b

Question 31

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

Answer 31

a

Question 32

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.

Answer 32

a

Question 33

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

Answer 33

d

Question 34

The replisome in prokaryotic replication consists of: a. a protein dimer b. a protein tetramer c. a multisubunit complex of at least 13 different proteins d. more than 100 separate proteins

Answer 34

c

Question 35

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 PPi. b. Nucleophilic attack of a 5' hydroxyl toward a nucleoside triphosphate, releasing PPi. c. Nucleophilic attack of a 3' hydroxyl toward a nucleoside triphosphate, releasing Pi. d. Nucleophilic attack of a 5' hydroxyl toward a nucleoside triphosphate, releasing Pi. e. More than one of these would work, since the mechanism is not universal.

Answer 35

a

Question 36

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.

Answer 36

a

Question 37

At the replisome of prokaryotic replication a. there are only two DNA Polymerase III molecules b. There are multiple copies of DNA Polymerase I c. Two molecules of Polymerase III are dedicated to lagging strand synthesis while one is dedicated to leading strand synthesis d. none of these

Answer 37

c

Question 38

A prokaryotic replisome typically contains three 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.

Answer 38

d

Question 39

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

Answer 39

a

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

Answer 40

b

Question 41

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

Answer 41

b

Question 42

Which of the following is true about clamp loaders? a. They are pentameric enzymes b. They serve to open up the sliding clamp and insert the DNA c. They are ATPases d. All of these

Answer 42

d

Question 43

Which of the following characteristics is not associated with E. coli primase? 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

Answer 43

d

Question 44

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.

Answer 44

b

Question 45

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

Answer 45

c

Question 46

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.

Answer 46

b

Question 47

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.

Answer 47

d

Question 48

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

Answer 48

d

Question 49

The enzyme that attaches the Okazaki fragments together is called a. ligase. b. primase. c. DNA polymerase I d. DNA polymerase III

Answer 49

a

Question 50

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.

Answer 50

c

Question 51

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.

Answer 51

e

Question 52

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

Answer 52

b

Question 53

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

Answer 53

a

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." a. True b. False

Answer 54

a

Question 55

DNA repair mechanisms are essentially the same whether the DNA has minor damage or major damage. a. True b. False

Answer 55

b

Question 56

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

Answer 56

a

Question 57

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

Answer 57

c

Question 58

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

Answer 58

b

Question 59

Which of the following enzymes is used to create AP sites? a. primase b. helicase c. ligase d. glycosylase

Answer 59

d

Question 60

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

Answer 60

b

Question 61

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

Answer 61

a

Question 62

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.

Answer 62

d

Question 63

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.

Answer 63

d

Question 64

Which of the following mechanisms can serve to repair double-stranded breaks in DNA? a. Non-homologous end joining b. recombination c. base excision repair d. nucleotide excision repair e. both a and b

Answer 64

e

Question 65

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

Answer 65

c

Question 66

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

Answer 66

b

Question 67

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

Answer 67

c

Question 68

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

Answer 68

b

Question 69

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.

Answer 69

b

Question 70

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.

Answer 70

c

Question 71

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

Answer 71

b

Question 72

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

Answer 72

b

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

Answer 73

d

Question 74

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.

Answer 74

a

Question 75

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.

Answer 75

a

Question 76

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

Answer 76

b

Question 77

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

Answer 77

a

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

Answer 78

d

Question 79

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

Answer 79

a

Question 80

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. a. True b. False

Answer 80

a

Question 81

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

Answer 81

a

Question 82

Telomerase activity in cancer cells may explain their longevity. a. True b. False

Answer 82

a

Question 83

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.

Answer 83

e

Question 84

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.

Answer 84

d

Question 85

_____ is the enzyme that directs the synthesis of DNA on an RNA template. a. Reverse transcriptase b. Phosphokinase c. Hydrolase d. Acyl transferase

Answer 85

a

Question 86

Explain how the different densities of DNA can be identified after subjecting a DNA sample to density-gradient centrifugation.

Answer 86

The density-gradient centrifugation technique depends on the fact that heavy 15N DNA forms a band at the bottom of a tube, and light 14N DNA appears at the top of the tube. DNA containing a 50-50 mixture of 14N and 15N appears at a position halfway between the two bands.

Question 87

The last nucleotide added to a growing DNA chain has a _____ on the sugar. a. 5'-hydroxyl b. 5'-triphosphate c. 3'-hydroxyl d. 3'-triphosphate

Answer 87

c

Question 88

_____ is an enzyme that introduces supercoiling into closed circular DNA. a. Primase b. DNA ligase c. Helicase d. DNA gyrase

Answer 88

d

Question 89

Errors in replication occur spontaneously only once in every _____ base pairs. a. 10^6 to 10^7 b. 10^9 to 10^10 c. 10^18 to 10^19 d. 10^21 to 10^22

Answer 89

b