ch 16 practice problems

14) Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately, what percentage of the nucleotides in this sample will be thymine? A) 12 B) 24 C) 31 D) 38 E) It cannot be determined from the information provided.

A

17) The DNA double helix has a uniform diameter because ________, which have two rings, always pair with ________, which have one ring. A) purines; pyrimidines B) pyrimidines; purines C) deoxyribose sugars; ribose sugars D) ribose sugars; deoxyribose sugars E) nucleotides; nucleoside triphosphates

A

18) What kind of chemical bond is found between paired bases of the DNA double helix? A) hydrogen B) ionic C) covalent D) sulfhydryl E) phosphate

A

20) 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 its A) sequence of bases. B) phosphate-sugar backbones. C) complementary pairing of bases. D) side groups of nitrogenous bases. E) different five-carbon sugars.

A

37) 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.

A

4) Avery and his colleagues purified various chemicals from pathogenic bacteria and showed that ________ was (were) the transforming agent. A) DNA B) protein C) lipids D) carbohydrates E) phage

A

53) Hershey and Chase used ________ to radioactively label the T2 phage's proteins. A) 35S B) 14C C) 222Ra D) 32P E) 92U

A

56) After DNA replication is completed, A) each new DNA double helix consists of one old DNA strand and one new DNA strand. B) each new DNA double helix consists of two new strands. C) one DNA double helix consists of two old strands and one DNA double helix consists of two new strands. D) each of the four DNA strands consists of some old strand parts and some new strand parts. E) there are four double helices.

A

11) Phage with labeled proteins or DNA was allowed to infect bacteria. It was shown that the DNA, but not the protein, entered the bacterial cells, and was therefore the genetic material. A. Frederick Griffith B. Alfred Hershey and Martha Chase C. Oswald Avery, Maclyn McCarty, and Colin MacLeod D. Erwin Chargaff E. Matthew Meselson and Franklin Stahl

B

13) When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result? A) The viral DNA will be radioactive. B) The viral proteins will be radioactive. C) The bacterial DNA will be radioactive. D) both A and B E) both A and C

B

2) In his transformation experiments, Griffith observed that 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. E) mice infected with a pathogenic strain of bacteria can spread the infection to other mice.

B

23) The strands that make up DNA are antiparallel. This means that 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 is positively charged and the other is negatively charged. E) one strand contains only purines and the other contains only pyrimidines.

B

26) 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 16.1 would you expect if the DNA was replicated in a conservative manner?

B

55) In a nucleotide, the nitrogenous base is attached to the sugar's ________ carbon and the phosphate group is attached to the sugar's ________ carbon. A) 1'; 2' B) 1'; 5' C) 2'; 3' D) 1'; 3' E) 2'; 1'

B

6) The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution. I. Avery, McCarty, and MacLeod II. Griffith III. Hershey and Chase IV. Meselson and Stahl V. Watson and Crick A) V, IV, II, I, III B) II, I, III, V, IV C) I, II, III, V, IV D) I, II, V, IV, III E) II, III, IV, V, I

B

62) 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 + T D) A = C E) G = T

B

10) Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA. A. Frederick Griffith B. Alfred Hershey and Martha Chase C. Oswald Avery, Maclyn McCarty, and Colin MacLeod D. Erwin Chargaff E. Matthew Meselson and Franklin Stahl

C

16) All of the following can be determined directly from X-ray diffraction photographs of crystallized DNA except the A) diameter of the helix. B) helical shape of DNA. C) sequence of nucleotides. D) spacing of the nitrogenous bases along the helix. E) number of strands in a helix.

C

54) Which of these is a difference between a DNA and an RNA molecule? A) DNA contains uracil, whereas RNA contains thymine. B) DNA is a polymer composed of nucleotides, whereas RNA is a polymer composed of nucleic acids. C) DNA is double-stranded, whereas RNA is single-stranded. D) DNA contains five-carbon sugars, whereas RNA contains six-carbon sugars. E) DNA contains nitrogenous bases, whereas RNA contains phosphate groups.

C

58) 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. E) bacteriophages injected DNA into bacteria.

C

19) Which of the following statements does not apply to the Watson and Crick model of DNA? A) The two strands of the DNA form a double helix. B) The distance between the strands of the helix is uniform. C) The framework of the helix consists of sugar-phosphate units of the nucleotides. D) The two strands of the helix are held together by covalent bonds. E) The purines form hydrogen bonds with pyrimidines.

D

1) For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. This is because A) proteins have a greater variety of three-dimensional forms than does DNA. B) proteins have two different levels of structural organization; DNA has four. C) proteins are made of 20 amino acids and DNA is made of four nucleotides. D) Only A and C are correct. E) A, B, and C are correct.

D

12) 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. Frederick Griffith B. Alfred Hershey and Martha Chase C. Oswald Avery, Maclyn McCarty, and Colin MacLeod D. Erwin Chargaff E. Matthew Meselson and Franklin Stahl

D

15) Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that A) the relative proportion of each of the four bases differs from species to species. B) the human genome is more complex than that of other species. C) the amount of A is always equivalent to T, and C to G. D) both A and C E) both B and C

D

25) 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 16.1 would be expected after one DNA replication in the presence of 14N?

D

59) 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 E) one low-density band

D

7) After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. The best evidence that the ability to fluoresce is a heritable trait would be an observation that 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.

D

8) 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 does not contain sulfur, whereas protein does. B) DNA contains phosphorus, but protein does not. C) DNA contains nitrogen, whereas protein does not. D) A and B only E) A, B, and C

D

24) Suppose one were provided with an actively dividing culture of E. coli bacteria to which radioactive thymine had been added. What would happen if a cell replicated 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.

E

21) In an analysis of the nucleotide composition of DNA, which of the following is true? A) A = C B) A = G and C = T C) A + C = G + T D) G + A = T + C E) both C and D

E

3) What does transformation involve 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) the type of semiconservative replication shown by DNA E) assimilation of external DNA into a cell

E

48) Which of these mechanisms ensures that the DNA sequence in the genome remains accurate? A) proofreading during DNA replication B) mismatch repair C) excision repair D) complementary base pairing during DNA replication E) all of the above

E

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) Meselson and Stahl already did this experiment. D) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive. E) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

E