Chapter 6 | Exam Questions – DNA Structure, Replication, and

Genetics, 6e (Hartwell)

Chapter 6 DNA Structure, Replication, and Recombination

1) Which of the following is not true of DNA?

A) It is acidic.

B) It contains deoxyribose.

C) It is found in cell nuclei.

D) It contains phosphate.

E) It contains amino acids.

2) The molecule of heredity is usually

A) RNA.

B) DNA.

C) protein.

D) carbohydrate.

E) None of the choices is correct.

3) The four subunits that make up DNA are called

A) phosphodiesters.

B) proteins.

C) nucleotides.

D) nucleosides.

E) polymers.

4) DNA is localized mainly in the

A) cell membrane.

B) endoplasmic reticulum.

C) vacuoles.

D) chromosomes.

E) Golgi.

5) The polarity of DNA synthesis is

A) 5'→3'.

B) 3'→5'.

C) 5'→2'.

D) 2'→5'.

6) In the Hershey and Chase experiment designed to determine the molecule of heredity, what was radiolabeled with 35S?

A) protein

B) DNA

C) RNA

D) rRNA

7) The ratio of ________ in DNA is 1:1.

A) guanine to adenine

B) adenine to thymine

C) cytosine to adenine

D) uracil to cytosine

8) X-ray data showed that the spacing between repeating units along the axis of the DNA helix is

A) 2.0 angstroms.

B) 3.4 angstroms.

C) 20 angstroms.

D) 34 angstroms.

9) X-ray data showed that the DNA helix undergoes one complete turn every

A) 2.0 angstroms.

B) 3.4 angstroms.

C) 20 angstroms.

D) 34 angstroms.

10) ________ bonds are responsible for the chemical affinity between A and T (or G and C) nucleotides.

A) Ionic

B) Covalent

C) Hydrogen

D) Hydrophobic

11) Which one of the following is not an element found in DNA?

A) oxygen

B) sulfur

C) nitrogen

D) phosphorous

E) hydrogen

12) ________-form DNA spirals to the right and is the major form of naturally occurring DNA molecules.

A) A

B) B

C) D

D) Y

E) Z

13) The nucleotide that is present in RNA but not DNA is

A) thymine.

B) uracil.

C) adenine.

D) cytosine.

E) guanine.

14) DNA replication occurs through a ________ process.

A) conservative

B) semiconservative

C) dispersive

D) transformative

15) During DNA replication, an incoming nucleotide is enzymatically joined to the preceding nucleotide by a(n) ________ bond.

A) hydrogen

B) ionic

C) phosphodiester

D) electrostatic

16) During early interphase the structure of a eukaryotic DNA chromosome is

A) a single continuous linear double helix.

B) a double helix undergoing semiconservative replication.

C) a double helix undergoing conservative replication.

D) single-stranded.

17) During the S phase of interphase, the state of a eukaryotic chromosome can be described as

A) a single continuous linear double helix.

B) a double helix replicating semiconservatively.

C) a double helix replicating conservatively.

D) a triple helix replicating semiconservatively.

E) two linear single-stranded molecules.

18) The step of DNA replication in which the replication proteins open up the double helix and prepare for complementary base pairing is called

A) initiation.

B) elongation.

C) termination.

D) translation.

E) translocation.

19) The step of DNA replication in which the proteins connect the correct sequence of nucleotides into a continuous new strand is called

A) initiation.

B) elongation.

C) termination.

D) translation.

E) translocation.

20) The step of DNA replication in which two replication forks moving in opposite directions may meet is called

A) initiation.

B) elongation.

C) termination.

D) translation.

E) translocation.

21) The group of enzymes able to relax supercoils in DNA is called

A) primases.

B) helicases.

C) topoisomerases.

D) telomeres.

E) ligases.

22) How many replication forks depart from an origin of replication?

A) one

B) two

C) three

D) four

23) The protein that progressively unwinds DNA ahead of each replication fork is called

A) primase.

B) helicase.

C) topoisomerase.

D) telomerase.

E) ligase.

24) In eukaryotic cells, replication proceeds from ________ origin(s) of replication.

A) zero

B) one

C) two

D) many

25) Eukaryotic chromosomes have evolved ________ at the ends of linear chromosomes to ensure the replication of the two ends of the chromosomes.

A) methylases

B) capping proteins

C) ligases

D) telomeres

E) single-stranded binding proteins

26) Which of the following is not involved in ensuring the accuracy of replication of a cell's genetic information?

A) redundancy of double-stranded DNA

B) repair enzymes

C) precision of replication machinery

D) DNA polymerase proofreading mechanism

E) restriction endonucleases

27) The process of ________ is extremely important in generating genetic diversity.

A) translation

B) transcription

C) recombination

D) transformation

28) Repair of heteroduplex regions formed during recombination can result in a 1:3 or 3:1 segregation of parental alleles, which indicates that ________ has occurred.

A) allelic exchange

B) gene conversion

C) crossing over

D) recombination

E) DNA replication

29) Recombination occurs during meiotic

A) anaphase

B) interphase

C) prophase

D) metaphase

30) Recombination involves the breakage and reunion of DNA molecules from

A) homologous nonsister chromatids.

B) homologous sister chromatids.

C) heterologous nonsister chromatids.

D) heterologous sister chromatids.

31) The nicking of DNA that initiates recombination during mitosis may be due to all of the following EXCEPT

A) instructions from the normal cell cycle program.

B) X-rays.

C) chemical damage.

D) physical damage.

E) radiation.

32) What radiolabeled substance did Hershey and Chase use to label the protein component of the bacteriophage in their study to determine whether protein or DNA was necessary for phage production?

A) nitrogen

B) carbon

C) sulfur

D) phosphorus

E) iodine

33) If 35% of the bases in a region of the mouse genome are cytosine, what percentage in that region are adenine?

A) 15%

B) 20%

C) 30%

D) 35%

E) cannot be determined

34) Two strains of S. cerevisae (yeast) are crossed. One has the genotype ABC and the other abc. Five sets of the resultant tetrads are noted below. In which set did a gene conversion event occur?

A) abc, aBc, AbC, aBC

B) abc, abc, ABC, ABC

C) aBc, aBc, AbC, AbC

D) abC, abc, ABc, ABC

E) Abc, Abc, aBC, aBC

35) Without ________ regions of the DNA during recombination, gene conversion could not occur.

A) homoduplex

B) heteroduplex

C) homotriplex

D) heterotriplex

36) Hershey and Chase relied on ________ to physically separate the infected bacterial cells from the phage ghosts.

A) radioactivity

B) gel filtration

C) ion exchange

D) centrifugation

37) Meselson and Stahl relied on equilibrium density gradient centrifugation in a ________ solution to resolve the DNA containing 14N from the DNA containing 15N.

A) radiolabeled phosphate

B) calcium chloride

C) radiolabeled nitrogen

D) sodium acetate

E) cesium chloride

38) The full chemical name of DNA is

A) derived nucleic acid.

B) dideoxyribonucleic acid.

C) denatured ribonucleic acid.

D) deoxyribonucleic acid.

39) Which term describes the ability of a substance to change the genetic characteristics of an organism?

A) transcription

B) translation

C) transformation

D) transposition

40) Which term is used to describe the overall 5′-to-3′ direction of linked nucleotides in a DNA chain?

A) complementarity

B) sequence

C) polarity

D) primacy

41) Which protein is needed to lay down a segment of RNA complementary to the DNA before replication can begin?

A) RNA polymerase II

B) primase

C) helicase

D) topoisomerase

E) ligase

42) How many origins of replication does the E. coli chromosome contain?

A) none

B) 1

C) 2

D) 3

E) many

43) A virus that infects bacterial cells is known as a

A) retrovirus

B) reovirus

C) bacteriophage

D) bacteriovirus

E) parvovirus

44) Which type of virus causes polio and AIDS?

A) retrovirus

B) reovirus

C) bacteriophage

D) adenovirus

E) parvovirus

45) Which protein relaxes supercoils by nicking the DNA?

A) topoisomerase

B) helicase

C) primase

D) ligase

E) telomerase

46) Given the following strand of DNA:

5′ CATAGCCTTA 3′

Which of the following sequences is the complementary DNA strand?

A) 5′ CATAGCCTTA 3′

B) 3′ GTATCGGAAT 5′

C) 5′ GTATCGGAAT 3′

D) 3′ GUAUCGGAAU 5′

E) 3′ CATAGCCTTA 5′

47) Which of the following is an example of a protein that can read the sequence of DNA without opening the double helix?

A) RNA polymerase

B) DNA polymerase

C) helicase

D) transcription factor

E) primase

48) Which of the following properties of RNA is most directly responsible for its ability to form complex shapes?

A) the presence of uracil instead of thymine

B) the fact that RNA is primarily double-stranded

C) the relative instability of RNA compared to DNA

D) the fact that RNA is primarily single-stranded

E) the substitution of deoxyribose in DNA with ribose in RNA

49) Suppose a region of DNA is 100 bp long. How many unique sequences could it potentially represent?

A) 1004

B) 4100

C) 400

D) 4,000

E) 10,000

50) Which of the following contains single-stranded DNA as its genetic material?

A) humans

B) E. coli

C) HIV

D) фX174

51) Transformation in bacteria results from the uptake of which molecule?

A) RNA

B) DNA

C) lipid

D) protein

E) polysaccharide

52) Z-form DNA is a ________ helix with ________ backbone.

A) right-handed; a smooth

B) left-handed; a smooth

C) right-handed; an irregular

D) left-handed; an irregular

53) Exposure of which of the following regions of a molecule of DNA permits the reading of DNA sequence without opening the double helix?

A) phosphate groups

B) phosphodiester bonds

C) major groove

D) minor groove

54) With respect to DNA structure, polarity means that

A) DNA nucleotides can be either positively or negatively charged.

B) the phosphate backbone of DNA is negatively charged.

C) DNA nucleotides can be charged or uncharged.

D) DNA strands have a 5′ direction and a 3′ direction.

55) Avery and colleagues purified a white substance as the transforming principle. Treating this substance with enzymes that destroyed RNA, protein, or polysaccharides did not affect its ability to transform cells, but enzyme that degrades DNA destroyed the transforming ability. These results suggested that

A) their transforming principle was not entirely pure.

B) the transforming principle appeared to be DNA.

C) the test for transformation was not accurate.

D) a single gene could transform bacterial cells.

E) both DNA and proteins are required for transformation.

56) If you repeated the Hershey and Chase experiment designed to determine the molecule of heredity using a virus with RNA as its genetic material, you would expect that

A) 35S-labeled protein would be transferred to infected cells.

B) 32P-labeled DNA would be transferred to infected cells.

C) 32P-labeled RNA would be transferred to infected cells.

D) 32P-labeled RNA would be transferred to phage ghosts.

E) 35S-labeled RNA would be transferred to infected cells.

57) Suppose the experiment of Meselson and Stahl was performed on a sample of 8 cells, each containing one copy of its circular double-stranded DNA genome, and that had been growing on normal 14N medium. You then grew the cells for 3 generations in medium containing 15N. The outcome would be

A) 8 cells with single-stranded DNA molecules with 14N, and 24 cells with single-stranded DNA molecules with 15N.

B) 16 cells with double-stranded DNA molecules with equal amounts of 14N and 15N, and 48 cells with double-stranded DNA molecules with 15N.

C) 8 cells with double-stranded DNA molecules with equal amounts of 14N and 15N, and 24 cells with double-stranded DNA molecules with 15N.

D) 8 cells with double-stranded DNA molecules with equal amounts of 14N and 15N, and 32 cells with double-stranded DNA molecules with 15N.

E) 65 cells with single-stranded DNA molecules with 15N.

58) Crossing-over that occurs only between two specific DNA target sites that are usually less than 200 base pairs long is called

A) mitotic recombination.

B) integrative recombination.

C) site-specific recombination.

D) homologous recombination.

E) non-random recombination.

59) A single DNA molecule contains two specific target sites separated by an intervening sequence. If site-specific recombination between these sites causes the intervening sequence to be released as a separate circular DNA molecule containing one target site, then the sites were oriented in

A) opposite directions causing excision.

B) the same direction causing excision.

C) opposite directions causing integration.

D) the same direction causing integration.

E) the same direction causing inversion.

60) Suppose that in the future, scientists identify bacteria on Mars and these organisms lack a site-specific recombination system. Which components would allow for site-specific recombination to occur in these bacteria?

A) FRT target sites and Flp recombinase

B) FRT target sites and Cas9 enzyme

C) an FRT target site and a loxP site

D) a synthetic homologous chromosome

61) Site-specific recombination systems, such as Flp recombinase/FRT sites, can function only in a single species.

62) Both Spo11 and Cas9 are enzymes that create double-strand breaks in DNA.

63) The normal functions of Spo11 and Cas9 enzymes are different because

A) Spo11 produces double-strand breaks during meiosis, whereas Cas9 functions during mitosis.

B) Spo11 produces site-specific double-strand breaks during meiosis, whereas Cas9 breaks DNA at random genomic locations.

C) Spo11 produces double-strand breaks in many genomic locations during meiosis, whereas Cas9 is targeted to specific sequences by a CRISPR RNA.

D) Spo11 produces double-strand breaks at sequences targeted by RNAs expressed during meiosis, whereas Cas9 has the ability to recognize DNA sequences without an RNA.

E) Spo11 is unique to yeast, whereas Cas9 occurs in most higher eukaryotes.

64) What is the correct order of these events in recombination that is resolved by the crossover pathway?

1. Double-strand break formation

2. Strand invasion

3. Resection

4. Resolution of the double Holliday junction

5. Branch migration

6. Formation of a double Holliday junction

A) 6, 1, 2, 5, 3, 4

B) 1, 2, 5, 3, 6, 4

C) 6, 4, 1, 2, 5, 3

D) 1, 3, 2, 6, 5, 4

E) 1, 2, 3, 5, 6, 4

65) During meiotic prophase in a eukaryotic cell, Spo11 initiates recombination by causing a double-strand break in DNA between Gene A and Gene B on one sister chromatid. Which of these events will occur prior to formation of a Holliday junction?

A) A heteroduplex forms due to pairing of Gene A and Gene B.

B) Resolvase cuts all four chromatids.

C) Spo11 causes a double-strand break in a nonsister chromatid.

D) Strand invasion causes one strand of the uncut chromatid to form a D loop.

E) Branch migration lengthens the heteroduplex region to include Gene A and Gene B.

66) A chromosome of genotype C D recombines with a homolog of genotype c d during meiosis when Spo11 produces a double-strand break between the two loci. If anticrossover helicase disentangles the invading strand, the likely outcome would be

A) two C D and two c d gametes.

B) two C d and two c D gametes.

C) one C D, one C d, one c D, and one c d gamete.

D) four C D gametes.

E) four c d gametes

67) Two strains of S. cerevisae (yeast) are crossed. One has the genotype A B and the other a b. Which statement correctly describes the tetrads that can be produced by one reciprocal exchange without gene conversion in the dihybrid?

A) Recombination occurs at the four-strand stage to produce a tetrad with A B, A B, a B, and a b chromosomes.

B) Recombination occurs at the four-strand stage to produce a tetrad with A B, A b, a B, and a b chromosomes.

C) Recombination occurs at the two-strand stage to produce a tetrad with A B, A b, a B, and a b chromosomes.

D) Recombination occurs at the two-strand stage to produce a tetrad with A b, A b, a B, and a B chromosomes.

68) The antiparallel polarity of the two DNA strands within the double helix affects DNA replication in that

A) it takes twice as long to replicate two strands sequentially from 5′ to 3′.

B) circular bacterial DNA does not have polarity, so a single strand can be copied twice.

C) DNA polymerases synthesizing both strands move in the direction of the replication fork, one strand is replicated discontinuously.

D) each portion of the double helix must be unwound twice so that both strands are replicated continuously.

69) If a chemical inhibitor of DNA ligase was added to bacterial cells after DNA replication initiation, the outcome would be

A) elongation of both strands would not occur without ligase to join new nucleotides together.

B) elongation would occur, but Okazaki fragments would not be joined together.

C) elongation of the lagging strand, but not the leading strand would occur.

D) normal replication would proceed as DNA ligase is not required for this process.

E) too many supercoils would build up in the DNA, resulting in a halting of elongation.

70) Homologous recombination occurs in a heterozygote in which alleles D and d differ by a single base pair. The D allele has a G at one position, whereas the d allele has a C at the same position. If branch migration causes heteroduplex formation across this position, what is the expected outcome?

A) Both D and d alleles will remain unchanged because G can base pair with C.

B) Mismatch repair will identify an abnormal G-G base pair and may convert the D allele to a d allele.

C) Mismatch repair will identify an abnormal C-G base pair and will ensure that the cell has two copies of each allele.

D) Mismatches will cause the Holliday junction to be unstable and to resolve by the noncrossover pathway.

71) Meselson and Weigle grew one strain of bacteriophage lambda with alleles A and B in heavy isotopes and another strain with alleles a and b in light isotopes. Both loci are located near the end of the viral chromosome. Which statement best describes their results and conclusions?

A) They visualized the broken chromosomes under a microscope and concluded that DNA was exchanged between light and heavy chromosomes during recombination.

B) They found a gradient of all densities of recombinant chromosomes and concluded that DNA was not exchanged between light and heavy chromosomes during recombination.

C) They found that some A b genetic recombinants were almost as dense as the A B parent chromosome and concluded that DNA was exchanged between light and heavy chromosomes during recombination.

D) They found that some A b genetic recombinants were almost as dense as the A B parent chromosome and concluded that DNA was not exchanged between light and heavy chromosomes during recombination.

72) If a cell had a single nonfunctional DNA repair enzyme, how would that cell be affected?

A) The cell could not possibly be viable without that DNA repair enzyme.

B) Mutations during DNA replication would not be repaired, so replication and therefore division would not be possible.

C) The cell's other DNA repair enzymes would most likely compensate and cell viability would be maintained.

D) DNA polymerase would re-replicate any damaged regions of DNA.

73) How does the antiparallel polarity of DNA strands contribute most to the integrity of genetic information?

A) A DNA double helix cannot be broken or degraded.

B) The antiparallel polarity of the strands means that replication occurs more quickly, decreasing the likelihood of DNA damage.

C) Hydrogen bonding between strands is very stable, so DNA bases cannot be not damaged by environmental agents.

D) Both antiparallel strands can be replicated continuously, which is more accurate than discontinuous replication.

E) Each antiparallel strand can serve as a template to produce the other strand in the event of DNA damage.