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front 1 1) In his transformation experiments, what did Griffith observe? A) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. B) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. C) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains. D) Mice infected with a pathogenic strain of bacteria can spread the infection to other mice.	back 1 Answer: A
front 2 2) How do we describe transformation in bacteria? 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) assimilation of external DNA into a cell	back 2 Answer: D
front 3 3) 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) evidence that DNA was passed from the heat-killed strain to the living strain B) evidence that protein passed from the heat-killed strain to the living strain C) especially bright phosphorescence in the living strain D) phosphorescence in descendants of the living cells	back 3 Answer: D
front 4 4) 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.	back 4 Answer: B

front 5 5) Which of the following investigators was (were) responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. A) Alfred Hershey and Martha Chase B) Oswald Avery, Maclyn McCarty, and Colin MacLeod C) Erwin Chargaff D) Matthew Meselson and Franklin Stahl	back 5 Answer: C
front 6 6) 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) 42% D) 58%	back 6 Answer: A
front 7 7) It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following? A) sequence of bases B) phosphate-sugar backbones C) complementary pairing of bases D) side groups of nitrogenous bases	back 7 Answer: A
front 8 8) 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	back 8 Answer: C

front 9 9) 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) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long. C) Although there are more nitrogens in a nucleotide, labeled phosphates actually have sixteen 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.	back 9 Answer: D
front 10 10) Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell? A) protein B) RNA C) ribosome D) DNA	back 10 Answer: D
front 11 11) In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _____ of the last nucleotide in the polymer. A) the 5' phosphate B) C6 C) the 3' OH D) a nitrogen from the nitrogen-containing base	back 11 Answer: C
front 12 12) Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons? 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.	back 12 Answer: B

front 13 13) What is meant by the description "antiparallel" regarding the strands 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 to 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.	back 13 Answer: B
front 14 14) Suppose you are provided with an actively dividing culture of E. 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) DNA in both daughter cells would be radioactive.	back 14 Answer: D
front 15 15) 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) Additional proofreading will occur. B) No replication fork will be formed. C) Replication will occur via RNA polymerase alone. D) Replication will require a DNA template from another source.	back 15 Answer: B
front 16 16) In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction? A) primase B) DNA ligase C) DNA polymerase III D) helicase	back 16 Answer: C

front 17 17) Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? A) the evolution of telomerase enzyme B) DNA polymerase that cannot replicate the leading strand template to its end C) gaps left at the 5' end of the lagging strand D) gaps left at the 3' end of the lagging strand because of the need for a primer	back 17 Answer: C
front 18 18) How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? A) It adds a single 5' cap structure that resists degradation by nucleases. B) It causes specific double-strand DNA breaks that result in blunt ends on both strands. C) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. D) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.	back 18 Answer: C
front 19 19) The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects _____. A) the low frequency of mutations occurring in this DNA B) continued evolution of telomeres C) that new mutations in telomeres have been advantageous D) a critical function of telomeres	back 19 Answer: D
front 20 20) At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' CCTAGGCTGCAATCC 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' GCCTAGG 3' B) 5' ACGTTAGG 3' C) 5' ACGUUAGG 3' D) 5' GCCUAGG 3'	back 20 Answer: C

front 21 21) In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act? A) nuclease, DNA polymerase III, RNA primase B) helicase, DNA polymerase I, DNA ligase C) DNA ligase, nuclease, helicase D) nuclease, DNA polymerase I, DNA ligase	back 21 Answer: D
front 22 22) In E. coli, 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	back 22 Answer: C
front 23 23) 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	back 23 Answer: A
front 24 24) The leading and the lagging strands 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	back 24 Answer: A

front 25 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) the polarity of the DNA molecule prevents addition of nucleotides at the 3' end C) replication must progress toward the replication fork D) DNA polymerase can add nucleotides only to the free 3' end	back 25 Answer: D
front 26 26) 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) unwinding of the double helix D) stabilizing single-stranded DNA at the replication fork	back 26 Answer: A
front 27 27) 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 joins Okazaki fragments together. C) It unwinds the parental double helix. D) It stabilizes the unwound parental DNA.	back 27 Answer: B
front 28 28) 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 DNA binding proteins	back 28 Answer: D

front 29 29) Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells cannot_____. A) replicate DNA B) undergo mitosis C) exchange DNA with other cells D) repair thymine dimers	back 29 Answer: D
front 30 30) Which of the following would you expect of a eukaryote lacking telomerase? A) a high probability of somatic cells becoming cancerous B) an inability to produce Okazaki fragments C) an inability to repair thymine dimers D) a reduction in chromosome length in gametes	back 30 Answer: D
front 31 35) Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____. A) allows variable width of the double helix B) permits complementary base pairing C) determines the tertiary structure of a DNA molecule D) determines the type of protein produced	back 31 Answer: B
front 32 36) Semiconservative replication involves a template. What is the template? A) single-stranded binding proteins B) DNA polymerase C) one strand of the DNA molecule D) an RNA molecule	back 32 Answer: C

front 33 37) DNA is synthesized through a process known as _____. A) semiconservative replication B) conservative replication C) translation D) transcription	back 33 Answer: A
front 34 38) Who performed classic experiments that supported the semiconservative model of DNA replication? A) Watson and Crick B) Meselson and Stahl C) Hershey and Chase D) Franklin and Wilkins	back 34 Answer: B
front 35 39) DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed? A) ribozymes B) DNA polymerase C) ATP D) deoxyribonucleotide triphosphates	back 35 Answer: B
front 36 40) What provides the energy for the polymerization reactions in DNA synthesis? A) ATP B) DNA polymerase C) breaking the hydrogen bonds between complementary DNA strands D) the deoxyribonucleotide triphosphate substrates	back 36 Answer: D

front 37 44) What is a telomere? A) the mechanism that holds two sister chromatids together B) DNA replication during telophase C) the site of origin of DNA replication D) the ends of linear chromosomes	back 37 Answer: D
front 38 45) Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging? A) Telomerase will speed up the rate of cell proliferation. B) Telomerase eliminates telomere shortening and retards aging. C) Telomerase shortens telomeres, which delays cellular aging. D) Telomerase would have no effect on cellular aging.	back 38 Answer: B
front 39 46) Telomere shortening is a problem in which types of cells? A) only prokaryotic cells B) only eukaryotic cells C) cells in prokaryotes and eukaryotes	back 39 Answer: B
front 40 47) Which of the following cells have reduced or very little active telomerase activity? A) most normal somatic cells B) most normal germ cells C) most cancer cells	back 40 Answer: A

front 41 48) Researchers found E. coli that had mutation rates one hundred times higher than normal. Which of the following is the most likely cause of these results? A) The single-stranded binding proteins were malfunctioning. B) There were one or more mismatches in the RNA primer. C) The proofreading mechanism of DNA polymerase was not working properly. D) The DNA polymerase was unable to add bases to the end of the growing nucleic acid chain.	back 41 Answer: C
front 42 49) In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell? A) The cell can be transformed to a cancerous cell. B) RNA may be used instead of DNA as inheritance material. C) The cell will become embryonic. D) DNA synthesis will continue by a new mechanism.	back 42 Answer: A
front 43 50) Which of the following statements describes a eukaryotic chromosome? A) a single strand of DNA B) a series of nucleosomes wrapped around two DNA molecules C) a chromosome with different numbers of genes in different cell types of an organism D) a single linear molecule of double-stranded DNA plus proteins	back 43 Answer: D
front 44 51) If a cell were unable to produce histone proteins, which of the following would be a likely effect? A) There would be an increase in the amount of "satellite" DNA produced during centrifugation. B) The cell's DNA couldn't be packed into its nucleus. C) Spindle fibers would not form during prophase. D) Amplification of other genes would compensate for the lack of histones.	back 44 Answer: B

front 45 52) Which of the following statements is true 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.	back 45 Answer: B
front 46 53) 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.	back 46 Answer: A
front 47 54) Which of the following 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) nucleosome, looped domain, 30-nm chromatin fiber D) 30-nm chromatin fiber, nucleosome, looped domain	back 47 Answer: A
front 48 55) Which of the following statements 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.	back 48 Answer: C

front 49 56) Which of the following is most critical for the association between histones and DNA? A) Histones are small proteins. B) Histones are highly conserved (that is, histones are very similar in every eukaryote). C) There are at least five different histone proteins in every eukaryote. D) Histones are positively charged.	back 49 Answer: D
front 50 57) In E. coli replication the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following would you expect? A) Replication would only occur on the leading strand. B) Replication would only occur on the lagging strand. C) Replication would not occur on either the leading or lagging strand. D) Replication would not be affected as the enzyme primase in involved with RNA synthesis.	back 50 Answer: C
front 51 58) Hershey and Chase used a DNA-based virus for their work. What would the results have been if they had used an RNA virus? A) With an RNA virus radioactive protein would have been in the final pellet. B) With an RNA virus radioactive RNA would have been in the final pellet. C) With an RNA virus neither sample would have had a radioactive pellet. D) With an RNA virus the protein shell would have been radioactive in both samples.	back 51 Answer: B
front 52 59) The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas? A) DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication. B) DNA is a polymer consisting of four monomers: adenine, thymine, guanine, and cytosine. C) DNA is the genetic material. D) Bacterial replication is fundamentally different from eukaryotic replication. The key shouldn’t be way longer than the distractors.	back 52 Answer: A

front 53

42) What is the difference between the leading strand and the lagging strand in DNA replication?

A) The leading strand is synthesized in the 3' → 5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5' → 3' direction in a continuous fashion.
B) The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.

C) The leading strand requires an RNA primer, whereas the lagging strand does not.
D) There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

back 53

Answer: B

front 54

43) What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?
A) Prokaryotic replication does not require a primer.
B) Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

C) DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semi-conservative.

D) DNA polymerases of prokaryotes can add nucleotides to both 3' and 5' ends of DNA strands while those of eukaryotes function only in the 5' → 3' direction.

back 54

Answer: B

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