Ch.14 DNA structure & Function

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? Question 9 options: 1) There is no radioactive isotope of nitrogen. 2) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long. 3) Although there are more nitrogens in a nucleotide, labeled phosphates actually have sixteen extra neutrons; therefore, they are more radioactive. 4) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

4) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

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? Question 14 options: 1) One of the daughter cells, but not the other, would have radioactive DNA. 2) Neither of the two daughter cells would be radioactive. 3) All four bases of the DNA would be radioactive. 4) DNA in both daughter cells would be radioactive.

4) DNA in both daughter cells would be radioactive.

A new DNA strand elongates only in the 5' to 3' direction because _____. Question 25 options: 1) DNA polymerase begins adding nucleotides at the 5' end of the template 2) the polarity of the DNA molecule prevents addition of nucleotides at the 3' end 3) replication must progress toward the replication fork 4) DNA polymerase can add nucleotides only to the free 3' end

4) DNA polymerase can add nucleotides only to the free 3' end

The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects _____. Question 19 options: 1) the low frequency of mutations occurring in this DNA 2) continued evolution of telomeres 3) that new mutations in telomeres have been advantageous 4) a critical function of telomeres

4) a critical function of telomeres

Which of the following would you expect of a eukaryote lacking telomerase? Question 30 options: 1) a high probability of somatic cells becoming cancerous 2) an inability to produce Okazaki fragments 3) an inability to repair thymine dimers 4) a reduction in chromosome length in gametes

4) a reduction in chromosome length in gametes

Which of the following statements describes a eukaryotic chromosome? Question 50 options: 4) a single linear molecule of double-stranded DNA plus proteins

4) a single linear molecule of double-stranded DNA plus proteins

How do we describe transformation in bacteria? Question 2 options: 1) the creation of a strand of DNA from an RNA molecule 2) the creation of a strand of RNA from a DNA molecule 3) the infection of cells by a phage DNA molecule 4) assimilation of external DNA into a cell

4) assimilation of external DNA into a cell

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? Question 3 options: 1) evidence that DNA was passed from the heat-killed strain to the living strain 2) evidence that protein passed from the heat-killed strain to the living strain 3) especially bright phosphorescence in the living strain 4) phosphorescence in descendants of the living cells

4) phosphorescence in descendants of the living cells

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells cannot_____. Question 29 options: 1) replicate DNA 2) undergo mitosis 3) exchange DNA with other cells 4) repair thymine dimers

4) repair thymine dimers

Which of the following help(s) to hold the DNA strands apart while they are being replicated? Question 28 options: 1) primase 2) ligase 3) DNA polymerase 4) single-strand DNA binding proteins

4) single-strand DNA binding proteins

What provides the energy for the polymerization reactions in DNA synthesis? Question 40 options: 4) the deoxyribonucleotide triphosphate substrates

4) the deoxyribonucleotide triphosphate substrates

What is a telomere? Question 44 options: 1) the mechanism that holds two sister chromatids together 2) DNA replication during telophase 3) the site of origin of DNA replication 4) the ends of linear chromosomes

4) the ends of linear chromosomes

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? Question 10 options: 1) protein 2) RNA 3) ribosome 4) DNA

4) DNA

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? Question 6 options: 1) 8% 2) 16% 3) 42% 4) 58%

1) 8%

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 Okazakifragments gave evidence for which of the following ideas? Question 59 options: 1) DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication.

1) DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication.

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? Question 49 options: 1) The cell can be transformed to a cancerous cell. 2) RNA may be used instead of DNA as inheritance material. 3) The cell will become embryonic. 4) DNA synthesis will continue by a new mechanism.

1) The cell can be transformed to a cancerous cell.

The leading and the lagging strands differ in that _____. Question 24 options: 1) 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 2) 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 3) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together 4) the leading strand is synthesized at twice the rate of the lagging strand

1) 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

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that _____. Question 23 options: 1) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose 2) the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups 3) ATP contains three high-energy bonds; the nucleoside triphosphates have two 4) ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells

1) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose

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 the figure above would you expect if the DNA was replicated in a conservative manner? Question 32 options: 1) A 2) B 3) C 4) D

2) B

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts? Question 4 options: 1) DNA contains sulfur, whereas protein does not. 2) DNA contains phosphorus, whereas protein does not. 3) DNA contains nitrogen, whereas protein does not. 4) DNA contains purines, whereas protein includes pyrimidines.

2) DNA contains phosphorus, whereas protein does not.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? Question 27 options: 1) It synthesizes RNA nucleotides to make a primer. 2) It joins Okazaki fragments together. 3) It unwinds the parental double helix. 4) It stabilizes the unwound parental DNA.

2) It joins Okazaki fragments together.

If a cell were unable to produce histone proteins, which of the following would be a likely effect? Question 51 options: 1) There would be an increase in the amount of "satellite" DNA produced during centrifugation. 2) The cell's DNA couldn't be packed into its nucleus. 3) Spindle fibers would not form during prophase. 4) Amplification of other genes would compensate for the lack of histones.

2) The cell's DNA couldn't be packed into its nucleus.

Hershey and Chase used a DNA-based virus for their work. What would the results have been if they had used an RNA virus? Question 58 options: 2) With an RNA virus, radioactive RNA would have been in the final pellet.

2) With an RNA virus radioactive RNA would have been in the final pellet.

Telomere shortening is a problem in which types of cells? Question 46 options: 1) only prokaryotic cells 2) only eukaryotic cells 3) cells in prokaryotes and eukaryotes

2) only eukaryotic cells

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____. Question 35 options: 1) allows variable width of the double helix 2) permits complementary base pairing 3) determines the tertiary structure of a DNA molecule 4) determines the type of protein produced

2) permits complementary base pairing

Refer to the figure above. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the new strand in the order that they will be added starting at the 3' end of the primer. Question 41 options: 1) C, A, G, C, A, G, A 2) T, C, T, G, C, T, G 3) A, G, A, C, G, A, C 4) G, T, C, G, T, C, T

3) A, G, A, C, G, A, C

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction? Question 16 options: 1) primase 2) DNA ligase 3) DNA polymerase III 4) helicase

3) DNA polymerase III

Semiconservative replication involves a template. What is the template? Question 36 options: 1) single-stranded binding proteins 2) DNA polymerase 3) one strand of the DNA molecule 4) an RNA molecule

3) one strand of the DNA molecule

Which of the following is most critical for the association between histones and DNA? Question 56 options: 4) Histones are positively charged.

4) Histones are positively charged.

In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act? Question 21 options: 1) nuclease, DNA polymerase III, RNA primase 2) helicase, DNA polymerase I, DNA ligase 3) DNA ligase, nuclease, helicase 4) nuclease, DNA polymerase I, DNA ligase

4) nuclease, DNA polymerase I, DNA ligase

In his transformation experiments, what did Griffith observe? Question 1 options: 1) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. 2) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. 3) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains. 4) Mice infected with a pathogenic strain of bacteria can spread the infection to other mice.

1) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the

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 _____. Question 34 options: 1) leading strands and Okazaki fragments 2) lagging strands and Okazaki fragments 3) Okazaki fragments and RNA primers 4) leading strands and RNA primers

1) leading strands and Okazaki fragments

Which of the following cells have reduced or very little active telomerase activity? Question 47 options: 1) most normal somatic cells

1) most normal somatic cells

Which of the following represents the order of increasingly higher levels of organization of chromatin? Question 54 options: 1) nucleosome, 30-nm chromatin fiber, looped domain

1) nucleosome, 30-nm chromatin fiber, looped domain

What is the function of topoisomerase? Question 26 options: 1) relieving strain in the DNA ahead of the replication fork 2) elongating new DNA at a replication fork by adding nucleotides to the existing chain 3) unwinding of the double helix 4) stabilizing single-stranded DNA at the replication fork

1) relieving strain in the DNA ahead of the replication fork

DNA is synthesized through a process known as _____. Question 37 options: 1) semiconservative replication 2) conservative replication 3) translation 4) transcription

1) semiconservative replication

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? Question 7 options: 1) sequence of bases 2) phosphate-sugar backbones 3) complementary pairing of bases 4) side groups of nitrogenous bases

1) sequence of bases

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? Question 39 options: 1) ribozymes 2) DNA polymerase 3) ATP 4) deoxyribonucleotide triphosphates

2) DNA polymerase

Which of the following statements is true of histones? Question 52 options: 1) Each nucleosome consists of two molecules of histone H1. 2) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together. 3) The carboxyl end of each histone extends outward from the nucleosome and is called a "histone tail." 4) Histones are found in mammals, but not in other animals or in plants or fungi.

2) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.

Who performed classic experiments that supported the semiconservative model of DNA replication? Question 38 options: 1) Watson and Crick 2) Meselson and Stahl 3) Hershey and Chase 4) Franklin and Wilkins

2) Meselson and Stahl

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? Question 15 options: 1) Additional proofreading will occur. 2) No replication fork will be formed. 3) Replication will occur via RNA polymerase alone. 4) Replication will require a DNA template from another source.

2) No replication fork will be formed.

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons? Question 12 options: 1) Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not. 2) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many. 3) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes. 4) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.

2) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication? Question 43 options: 1) Prokaryotic replication does not require a primer. 2) Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication. 3) DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semi-conservative. 4) 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.

2) Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

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? Question 45 options: 2) Telomerase eliminates telomere shortening and retards aging.

2) Telomerase eliminates telomere shortening and retards aging.

What is meant by the description "antiparallel" regarding the strands that make up DNA? Question 13 options: 1) The twisting nature of DNA creates nonparallel strands. 2) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. 3) Base pairings create unequal spacing between the two DNA strands. 4) One strand contains only purines and the other contains only pyrimidines.

2) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

What is the difference between the leading strand and the lagging strand in DNA replication? Question 42 options: 1) 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. 2) The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction. 3) The leading strand requires an RNA primer, whereas the lagging strand does not. 4) There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

2) The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? Question 20 options: 1) 5' G C C T A G G 3' 2) 5' A C G T T A G G 3' 3) 5' A C G U U A G G 3' 4) 5' G C C U A G G 3'

3) 5' A C G U U A G G 3'

In an analysis of the nucleotide composition of DNA, which of the following will be found? Question 8 options: 1) A = C 2) A = G and C = T 3) A + C = G + T 4) G + C = T + A

3) A + C = G + T

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. Question 5 options: 1) Alfred Hershey and Martha Chase 2) Oswald Avery, Maclyn McCarty, and Colin MacLeod 3) Erwin Chargaff 4) Matthew Meselson and Franklin Stahl

3) Erwin Chargaff

Which of the following statements describes chromatin? Question 55 options: 1) Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA. 2) Both heterochromatin and euchromatin are found in the cytoplasm. 3) Heterochromatin is highly condensed, whereas euchromatin is less compact. 4) Euchromatin is not transcribed, whereas heterochromatin is transcribed.

3) Heterochromatin is highly condensed, whereas euchromatin is less compact.

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? Question 18 options: 1) It adds a single 5' cap structure that resists degradation by nucleases. 2) It causes specific double-strand DNA breaks that result in blunt ends on both strands. 3) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. 4) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.

3) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

After the first replication was observed in their experiments testing the nature of DNA replication, Meselson and Stahl could be confident of which of the following conclusions? Question 33 options: 1) Replication is semi-conservative. 2) Replication is not dispersive. 3) Replication is not conservative

3) Replication is not conservative

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 DNApolymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following would you expect? Question 57 options: 3) Replication would not occur on either the leading or lagging strand.

3) Replication would not occur on either the leading or lagging strand.

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? Question 48 options: 3) The proofreading mechanism of DNA polymerase was not working properly.

3) The proofreading mechanism of DNA polymerase was not working properly.

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? Question 17 options: 1) the evolution of telomerase enzyme 2) DNA polymerase that cannot replicate the leading strand template to its 5' end 3) gaps left at the 5' end of the lagging strand 4) gaps left at the 3' end of the lagging strand because of the need for a primer

3) gaps left at the 5' end of the lagging strand

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. Question 11 options: 1) the 5' phosphate 2) C6 3) the 3' OH 4) a nitrogen from the nitrogen-containing base

3) the 3' OH

In E. coli, what is the function of DNA polymerase III? Question 22 options: 1) to unwind the DNA helix during replication 2) to seal together the broken ends of DNA strands 3) to add nucleotides to the 3' end of a growing DNA strand 4) to degrade damaged DNA molecules

3) to add nucleotides to the 3' end of a growing DNA strand

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 the figure above would be expected after one round of DNA replication in the presence of 14N? Question 31 options: 1) A 2) B 3) C 4) D

4 (D)

Why do histones bind tightly to DNA? Question 53 options: 1) Histones are positively charged, and DNA is negatively charged. 2) Histones are negatively charged, and DNA is positively charged. 3) Both histones and DNA are strongly hydrophobic. 4) Histones are covalently linked to the DNA.

Histones are positively charged, and DNA is negatively charged.