Deck 13: The Molecular Basis of Inheritance

Question 1

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

A) No proofreading will occur.
B) The DNA strands at the origin of replication will separate, but replication will not progress.
C) The DNA will supercoil.
D) Replication will require a DNA template from another source.

Answer 1

B

Question 2

An Okazaki fragment has which of the following arrangements?

A) primase, polymerase, ligase
B) 3' RNA nucleotides, DNA nucleotides 5'
C) 5' RNA nucleotides, DNA nucleotides 3'
D) DNA polymerase I, DNA polymerase III
E) 5' DNA to 3'

Answer 2

C

Question 3

Suppose you are provided with an actively dividing culture of Escherichia coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

A) One of the daughter cells, but not the other, would have radioactive DNA.
B) Neither of the two daughter cells would be radioactive.
C) All four bases of the DNA would be radioactive.
D) Radioactive thymine would pair with nonradioactive guanine.
E) DNA in both daughter cells would be radioactive.

Answer 3

E

Question 4

What is the function of DNA polymerase III?

A) to unwind the DNA helix during replication
B) to seal together the broken ends of DNA strands
C) to add nucleotides to the 3' end of a growing DNA strand
D) to degrade damaged DNA molecules
E) to rejoin the two DNA strands (one new and one old) after replication

Question 5

In his transformation experiments, what did Griffith observe?

A) Mutant mice were resistant to bacterial infections.
B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
C) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
D) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

Question 6

In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. Which of the following investigators was (were) responsible for this discovery?

A) Frederick Griffith
B) Alfred Hershey and Martha Chase
C) Oswald Avery
D) Erwin Chargaff
E) Matthew Meselson and Franklin Stahl

Question 7

After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?

A) DNA passed from the heat-killed strain to the living strain.
B) Protein passed from the heat-killed strain to the living strain.
C) The phosphorescence in the living strain is especially bright.
D) Descendants of the living cells are also phosphorescent.
E) Both DNA and protein passed from the heat-killed strain to the living strain.

Question 8

How is transformation in bacteria most accurately described?

A) the creation of a strand of DNA from an RNA molecule
B) the creation of a strand of RNA from a DNA molecule
C) the infection of cells by a phage DNA molecule
D) the type of semiconservative replication shown by DNA
E) assimilation of external DNA into a cell

Question 9

What is meant by the description "antiparallel" regarding the two strands of nucleic acids that make up DNA?

A) The twisting nature of DNA creates nonparallel strands.
B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
C) Base pairings create unequal spacing between the two DNA strands.
D) One strand contains only purines and the other contains only pyrimidines.

Question 10

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

A) DNA contains sulfur, whereas protein does not.
B) DNA contains phosphorus, whereas protein does not.
C) DNA contains nitrogen, whereas protein does not.
D) DNA contains purines, whereas protein includes pyrimidines.
E) RNA includes ribose, whereas DNA includes deoxyribose sugars.

Question 11

Which of the following statements describes one difference between DNA replication in prokaryotes and DNA replication in eukaryotes?

A) Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.
B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.
D) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.
E) Prokaryotes have telomeres, and eukaryotes do not.

Question 12

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel structures. How could these arise?

A) replication followed by mitosis
B) replication without separation
C) meiosis followed by mitosis
D) fertilization by multiple sperm
E) special association with histone proteins

Question 13

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

A) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.
B) the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups.
C) ATP contains three high-energy bonds; the nucleoside triphosphates have two.
D) ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells.
E) triphosphate monomers are active in the nucleoside triphosphates, but not in ATP.

Question 14

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A) A = C
B) A = G and C = T
C) A + C = G + T
D) G + C = T + A

Question 15

At a specific area of a chromosome, the following sequence of nucleotides is present where the chain opens to form a replication fork:
3'-C C T A G G C T G C A A T C C-5'
An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

A) 5'-G C C T A G G-3'
B) 3'-G C C T A G G-5'
C) 5'-A C G T T A G G-3'
D) 5'-A C G U U A G G-3'
E) 5'-G C C U A G G-3'

Question 16

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information based on which of the following characteristics?

A) the sequence of bases
B) phosphate-sugar backbones
C) complementary pairing of bases
D) different five-carbon sugars

Question 17

In which order do the necessary enzymes act to repair a thymine dimer by nucleotide excision repair?

A) nuclease, DNA polymerase, RNA primase
B) helicase, DNA polymerase, DNA ligase
C) DNA ligase, nuclease, helicase
D) DNA polymerase, RNA polymerase, DNA ligase
E) nuclease, DNA polymerase, DNA ligase

Question 18

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

A) 8%
B) 16%
C) 31%
D) 42%

Question 19

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

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

Question 20

Which of the following characteristics can be determined directly from X-ray diffraction photographs of crystallized DNA?

A) the diameter of the helix
B) the rate of replication
C) the sequence of nucleotides
D) the frequency of A versus T nucleotides

Question 21

Which of the following statements best describes the eukaryotic chromosome?

A) It is composed of DNA alone.
B) The nucleosome is its most basic functional subunit.
C) The number of genes on each chromosome is different in different cell types of an organism.
D) It consists of a single linear molecule of double-stranded DNA plus proteins.

Question 22

Which of the following statements correctly describes chromatin?

A) Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.
B) Both heterochromatin and euchromatin are found in the cytoplasm.
C) Heterochromatin is highly condensed, whereas euchromatin is less compact.
D) Euchromatin is not transcribed, whereas heterochromatin is transcribed.

Question 23

Which of the following enzymes synthesizes short segments of RNA?

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

Question 24

Which of the following lists of structures correctly represents the order of increasingly higher levels of organization of chromatin?

A) nucleosome, 30-nm chromatin fiber, looped domain
B) looped domain, 30-nm chromatin fiber, nucleosome
C) looped domain, nucleosome, 30-nm chromatin fiber
D) nucleosome, looped domain, 30-nm chromatin fiber
E) 30-nm chromatin fiber, nucleosome, looped domain

Question 25

A new DNA strand elongates only in the 5' to 3' direction because

A) DNA polymerase begins adding nucleotides at the 5' end of the template.
B) Okazaki fragments prevent elongation in the 3' to 5' direction.
C) replication must progress toward the replication fork.
D) DNA polymerase can only add nucleotides to the free 3' end.

Question 26

Given the damage caused by UV radiation, the kind of gene affected in those with xeroderma pigmentosum is one whose product is involved with

A) mending of double-strand breaks in the DNA backbone.
B) breakage of cross-strand covalent bonds.
C) the ability to excise damage to single-stranded DNA and replace it.
D) the removal of damaged areas of double-stranded DNA.
E) causing affected skin cells to undergo apoptosis.

Question 27

During DNA replication, which of the following enzymes separates the DNA strands during replication?

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

Question 28

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

A) The cell's DNA couldn't be packed into its nucleus.
B) Spindle fibers would not form during prophase.
C) Expression of other genes would compensate for the lack of histones.
D) DNA polymerase I would not function properly.

Question 29

During DNA replication, which of the following enzymes covalently connects segments of DNA?

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

Question 30

Which of the following statements correctly describes one characteristic of histones?

A) Each nucleosome consists of two molecules of histone H1.
B) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
C) The carboxyl end of each histone extends outward from the nucleosome and is called a "histone tail."
D) Histones are found in mammals, but not in other animals or in plants or fungi.

Question 31

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?

A) They cannot replicate DNA.
B) They cannot undergo mitosis.
C) They cannot exchange DNA with other cells.
D) They cannot repair thymine dimers.
E) They do not recombine homologous chromosomes during meiosis.

Question 32

Which of the following modifications is most likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?

A) altering the nucleotide sequence of the DNA fragment without adding or removing nucleotides
B) radioactively labeling the cytosine bases within the DNA fragment
C) increasing the length of the DNA fragment
D) leaving the length of the DNA fragment the same

Question 33

Which of the following sets of materials is required by both eukaryotes and prokaryotes for DNA replication?

A) double-stranded DNA, four kinds of DNA nucleotides, primers, origins of replication
B) topoisomerases, telomerases, polymerases
C) G-C rich regions, polymerases, chromosome nicks
D) nucleosome loosening, four kinds of DNA nucleotides, four kinds of RNA nucleotides
E) ligase, primers, nucleases

Question 34

What is the function of topoisomerase?

A) relieving strain in the DNA ahead of the replication fork
B) elongating new DNA at a replication fork by adding nucleotides to the existing chain
C) adding methyl groups to bases of DNA
D) unwinding of the double helix
E) stabilizing single-stranded DNA at the replication fork

Question 35

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

A) DNA without attached histones
B) DNA with H1 only
C) the 10-nm chromatin fiber
D) the 30-nm chromatin fiber

Question 36

The leading and the lagging strands of DNA formed during DNA replication differ in that

A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
B) the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.
C) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.
D) the leading strand is synthesized at twice the rate of the lagging strand.

Question 37

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

A) primase
B) ligase
C) DNA polymerase
D) single-strand binding proteins
E) nuclease

Question 38

Why do histones bind tightly to DNA?

A) Histones are positively charged, and DNA is negatively charged.
B) Histones are negatively charged, and DNA is positively charged.
C) Both histones and DNA are strongly hydrophobic.
D) Histones are covalently linked to the DNA.
E) Histones are highly hydrophobic, and DNA is hydrophilic.

Question 39

During DNA replication, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

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

Question 40

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

A) It synthesizes RNA nucleotides to make a primer.
B) It catalyzes the lengthening of telomeres.
C) It joins Okazaki fragments together.
D) It unwinds the parental double helix.
E) It stabilizes the unwound parental DNA.

Question 41

Assume that you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzyme X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y, but not for X. Your strategy should be to

A) insert the fragments cut with restriction enzyme X directly into the plasmid without cutting the plasmid.
B) cut the plasmid with restriction enzyme X and insert the fragments cut with restriction enzyme Y into the plasmid.
C) cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with the same enzyme.
D) cut the plasmid twice with restriction enzyme Y and ligate the two fragments onto the ends of the DNA fragments cut with restriction enzyme X.
E) cut the plasmid with restriction enzyme X and then insert the gene into the plasmid.

Question 42

Why is it so important to be able to amplify DNA fragments when studying genes?

A) DNA fragments are too small to use individually.
B) A gene may represent only a millionth of the cell's DNA.
C) Restriction enzymes cut DNA into fragments that are too small.
D) A clone requires multiple copies of each gene per clone.
E) It is important to have multiple copies of DNA in the case of laboratory error.

Question 43

Please use the following information to answer the question(s) below.
A group of six students has taken samples of their own cheek cells, purified the DNA, and used a restriction enzyme known to cut at zero, one, or two sites in a particular gene of interest.
Why might they be conducting such an experiment?

A) to find the location of this gene in the human genome
B) to prepare to isolate the chromosome on which the gene of interest is found
C) to find which of the students has which alleles
D) to collect population data that can be used to assess natural selection

Question 44

What is the most logical sequence of steps for splicing foreign DNA into a plasmid and inserting the plasmid into a bacterium?

A) Transform bacteria with a recombinant DNA molecule. Cut the plasmid DNA using restriction enzymes. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments. Extract plasmid DNA from bacterial cells. Use ligase to seal plasmid DNA to nonplasmid DNA.
B) Cut the plasmid DNA using restriction enzymes. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments. Use ligase to seal plasmid DNA to nonplasmid DNA. Extract plasmid DNA from bacterial cells. Transform bacteria with a recombinant DNA molecule.
C) Extract plasmid DNA from bacterial cells. Cut the plasmid DNA using restriction enzymes. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments. Use ligase to seal plasmid DNA to nonplasmid DNA. Transform bacteria with a recombinant DNA molecule.
D) Extract plasmid DNA from bacterial cells. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments. Use ligase to seal plasmid DNA to nonplasmid DNA. Transform bacteria with a recombinant DNA molecule. Cut the plasmid DNA using restriction enzymes.

Question 45

Figure 13.1
Figure 13.3
Which enzyme was used to produce the molecule in Figure 13.3?

A) ligase
B) a restriction enzyme
C) RNA polymerase
D) DNA polymerase

Question 46

How does a bacterial cell protect its own DNA from restriction enzymes?

A) by adding methyl groups to adenines and cytosines
B) by using DNA ligase to seal the bacterial DNA into a closed circle
C) by adding histones to protect the double-stranded DNA
D) by forming "sticky ends" of bacterial DNA to prevent the enzyme from attaching

Question 47

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

A) DNA polymerase can join new nucleotides only to the 3' end of a preexisting strand.
B) Helicases and single-strand binding proteins work at the 5' end.
C) The origins of replication occur only at the 5' end.
D) DNA ligase works only in the 3' → 5' direction.

Question 48

Figure 13.1
Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

A) Replication is semiconservative.
B) Replication is not dispersive.
C) Replication is not semiconservative.
D) Replication is not conservative.
E) Replication is neither dispersive nor conservative.

Question 49

In his work with pneumonia-causing bacteria and mice, Griffith found that

A) the protein coat from pathogenic cells was able to transform nonpathogenic cells.
B) heat-killed pathogenic cells caused pneumonia.
C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
D) the polysaccharide coat of bacteria caused pneumonia.

Question 50

Figure 13.1
Figure 13.4
The segment of DNA shown in Figure 13.4 has restriction sites I and II, which create restriction fragments A, B, and C. Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments?

A)
B)
C)
D)
E)

Question 51

Please use the following information to answer the question(s) below.
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to the antibiotics ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics.
Bacteria containing a plasmid into which the eukaryotic gene has integrated would grow

A) in the nutrient broth only.
B) in the nutrient broth and the tetracycline broth only.
C) in the nutrient broth, the ampicillin broth, and the tetracycline broth.
D) in all four types of broth.
E) in the ampicillin broth and the nutrient broth.

Question 52

Please use the following information to answer the question(s) below.
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to the antibiotics ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics.
Bacteria that contain the plasmid, but not the eukaryotic gene, would grow

A) in the nutrient broth plus ampicillin, but not in the broth containing tetracycline.
B) only in the broth containing both antibiotics.
C) in the broth containing tetracycline, but not in the broth containing ampicillin.
D) in all four types of broth.
E) in the nutrient broth without antibiotics only.

Question 53

Please use the following information to answer the question(s) below.
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to the antibiotics ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics.
Bacteria that do not take up any plasmids would grow on which media?

A) the nutrient broth only
B) the nutrient broth and the tetracycline broth
C) the nutrient broth and the ampicillin broth
D) the tetracycline broth and the ampicillin broth
E) all three broths

Question 54

Please use the following information to answer the question(s) below.
A group of six students has taken samples of their own cheek cells, purified the DNA, and used a restriction enzyme known to cut at zero, one, or two sites in a particular gene of interest.
Analysis of the data obtained shows that two students each have two fragments, two students each have three fragments, and two students each have one only. What does this demonstrate?

A) Each pair of students has a different gene for this function.
B) The two students who have two fragments have one restriction site in this region.
C) The two students who have two fragments have two restriction sites within this gene.
D) Each of these students is heterozygous for this gene.

Question 55

Figure 13.1
A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 13.1 would you expect after one round of DNA replication if the DNA was replicated in a conservative manner?

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

Question 56

Figure 13.1
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

A) There is no radioactive isotope of nitrogen.
B) Avery et al. have already concluded that this experiment showed inconclusive results.
C) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
D) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

Question 57

Figure 13.1
Figure 13.2
In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine). After several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. Figure 13.2 represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results?

A) There are two replication forks going in opposite directions.
B) Thymidine is being added only where the DNA strands are farthest apart.
C) Thymidine is being added only at the very beginning of replication.
D) Replication proceeds in one direction only.

Question 58

Figure 13.1
In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in Figure 13.1 would be expected after one round of DNA replication in the presence of 14N?

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

Question 59

Figure 13.1
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

A) leading strands and Okazaki fragments.
B) lagging strands and Okazaki fragments.
C) Okazaki fragments and RNA primers.
D) leading strands and RNA primers.
E) RNA primers and mitochondrial DNA.

Question 60

Which of the following statements accurately describes why Taq polymerase is used in PCR?

A) It is heat stable and can withstand the heating step of PCR.
B) Only minute amounts are needed for each cycle of PCR.
C) It binds more readily than other polymerases to the primers.
D) It has regions that are complementary to the primers.
E) It is heat stable, and it binds more readily than other polymerases to the primers.

Question 61

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

A) A = G
B) A + G = C + T
C) A + T = G + C
D) A = C

Question 62

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

A) one high-density and one low-density band
B) one intermediate-density band
C) one high-density and one intermediate-density band
D) one low-density and one intermediate-density band

Question 63

The elongation of the leading strand during DNA synthesis

A) progresses away from the replication fork.
B) occurs in the 3' → 5' direction.
C) produces Okazaki fragments.
D) depends on the action of DNA polymerase.

Question 64

Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme?

A) AAGG TTCC
B) GGCC CCGG
C) ACCA TGGT
D) AAAA TTTT

Question 65

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. After adding some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has the student probably left out of the mixture?

A) DNA polymerase
B) DNA ligase
C) Okazaki fragments
D) primase

Question 66

In a nucleosome, the DNA is wrapped around

A) polymerase molecules.
B) ribosomes.
C) histones.
D) a thymine dimer.

Question 67

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

A) nuclease, DNA polymerase, DNA ligase
B) topoisomerase, primase, DNA polymerase
C) topoisomerase, helicase, single-strand binding protein
D) DNA ligase, replication fork proteins, adenylyl cyclase