Molecular Inheritance
1. Incorrect In an important experiment, radioactively labeled bacteriophages were allowed to infect bacteria. In the first
trial, the phages contained radioactive DNA, and radioactivity was detected in the bacteria. Next, other phages containing
radioactive protein were allowed to infect bacteria, and radioactivity was not detected in the bacteria. These experiments led
to the conclusion that _____. (p. 289)
Your answer: bacteriophages can infect bacteria
The correct answer: the genes of this phage were made of DNA
No. This was known, but it does not show what the viral genetic material was.
2. Correct In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, the
key finding was that _____. (p. 289)
Your answer: radioactively labeled phosphorus remained in the infected bacteria but not in the bacteriophage bodies
Correct. When the bacteria had been infected with T2 phage whose DNA was tagged with radioactive phosphorus, the pellet
of mainly bacterial material contained most of the radioactivity, indicating that the labeled phage genetic material had
entered the host cells.
3. Incorrect Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA
of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have
_____. (p. 289)
Your answer: the protein of T2 and the DNA of T4
The correct answer: the protein and DNA of T4
No. Viral protein does not contain the information for the production of more viral protein.
4. Correct Chargaff found that for DNA _____. (p. 290)
Your answer: the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
Correct. This is a result of specific base pairing and of DNA's double-helix structure.
5. Correct Which one of the following lists the four bases contained in DNA? (p. 290)
Your answer: adenine, guanine, cytosine, thymine
Correct. DNA contains four bases: adenine, guanine, cytosine, and thymine.
6. Correct Chargaff's rule (the amount of adenine in DNA equals the amount of thymine, and so forth) was the key to
understanding _____. (p. 292)
Your answer: how the nitrogenous bases pair in the double helix.
Correct. Chargaff's finding that the amount of A = T and the amount of G = C led Watson and Crick to an understanding of
the base-pairing relationships as they sought to understand the structure of DNA.
7. Correct During Griffith's experiments with pneumococci in mice, material from __________ bacteria transformed
__________ bacteria. (p. 288)
Your answer: heat-killed virulent ... living nonvirulent
Correct. Griffith found that some of the living nonvirulent cells were converted to the virulent form.
8. Correct Avery's 1943 experiment showed that DNA _____. (p. 288)
Your answer: was the substance that transformed the bacteria in Griffith's experiment
Correct. Avery and his colleagues announced that the transforming agent was DNA.
9. Correct Which of the following is correct? (p. 292)
Your answer: A forms two hydrogen bonds with T; G forms three hydrogen bonds with C.
Correct. This is a consequence of the characteristics of the bases.
10. Correct The two strands of a DNA double helix are antiparallel. This means that _____. (p. 296)
Your answer: one strand runs in the 5' --> 3' direction and the other runs in the 3' --> 5' direction
Correct. This allows the two strands to fit together properly.
11. Correct One strand of a DNA molecule has the base sequence ATAGGT. The complementary base sequence on the
other strand of DNA will be _____. (p. 292)
Your answer: TATCCA
Correct. A always pairs with T, and G with C.
12. Correct The two sugar-phosphate strands of a DNA molecule are joined to each other through _____. (p. 292)
Your answer: hydrogen bonds between nucleotide bases
Correct. The two sugar-phosphate strands of a DNA molecule are held together by hydrogen bonding between the
nitrogenous bases, which are paired in the interior of the helix.
13. Correct Who is generally credited with discovering that the DNA molecule is constructed as a double helix? (p. 291)
Your answer: Watson and Crick
Correct. In April 1953, Watson and Crick published a one-page paper in Nature magazine elucidating their molecular model
for DNA, the double helix.
14. Correct In a eukaryotic cell, DNA _____. (p. 290)
Your answer: contains the sugar deoxyribose
Correct. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate
group.
15. Correct Which one of the following describes a nucleotide most completely? (p. 290)
Your answer: nitrogen base, five-carbon sugar, and a phosphate group
Correct. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate
group.
16. Correct The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which these
two DNAs are the same is that _____. (p. 290)
Your answer: both have a sugar-phosphate backbone
Correct. All DNA occurs as a double helix with two sugar-phosphate backbones that are antiparallel to each other.
17. Correct Which one of the following accurately reflects complementary base pairing in the DNA molecule? (p. 292)
Your answer: guanine–cytosine
Correct. Watson and Crick reasoned that there must be additional specificity in base pairing. Adenine can form two
hydrogen bonds with thymine, and only thymine; guanine forms three hydrogen bonds with cytosine, and only cytosine.
18. Correct Which one of the following is NOT true about double-stranded DNA? (p. 290)
Your answer: Adenine and uracil are present in equal amounts.
Correct. Uracil does NOT occur in DNA.
19. Correct The information in DNA is contained in _____. (p. 292)
Your answer: the sequence of nucleotides along the length of one strand of the DNA molecule
Correct. Although base-pairing rules dictate the combinations of nitrogenous bases forming the "rungs" of the double helix,
they do not restrict the sequence of nucleotides along each strand, and the linear sequence of bases can be varied in countless
ways.
20. Correct Prokaryotes replicate their DNA __________ eukaryotes do. (p. 295)
Your answer: much faster than
Correct. The rate of elongation is about 500 nucleotides per second in bacteria and about 50 per second in human cells.
21. Correct Which one of the following is NOT a component of a nucleotide? (p. 290)
Your answer: Mg2+
Correct. Mg2+ is NOT part of a nucleotide. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the
sugar deoxyribose, and a phosphate group.
22. Correct What technique was most helpful to Watson and Crick? (p. 291)
Your answer: X-ray crystallography
Correct. Watson and Crick based their model of DNA on data they were able to extract from Franklin's X-ray diffraction
photo.
23. Correct Which one of the following statements does NOT apply to the Watson-Crick model for DNA? (p. 291)
Your answer: The two strands of the helix are held together by covalent bonds.
Correct. The two strands of the helix are held together by HYDROGEN bonding between the nitrogenous bases, which are
paired in the interior of the helix.
24. Correct In DNA, the weakest bonds are between _____. (p. 292)
Your answer: two nitrogenous bases
Correct. The two sugar-phosphate strands of a DNA molecule are held together by hydrogen bonding between the
nitrogenous bases, which are paired in the interior of the helix.
25. Correct 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 _____. (p. 292)
Your answer: sequence of bases
Correct. Although base-pairing rules dictate the combinations of nitrogenous bases forming the "rungs" of the double helix,
they do not restrict the sequence of nucleotides along each strand, and the linear sequence of bases can be varied in countless
ways.
26. Correct One strand of DNA has the following sequence of nucleotides: 3'-ATTCGCTAT-5' The base sequence on the
other strand of DNA would be _____. (p. 296)
Your answer: 5'-TAAGCGATA-3'
Correct. Adenine can form two hydrogen bonds with thymine, and only thymine; guanine forms three hydrogen bonds with
cytosine, and only cytosine.
27. Correct Which description of DNA replication is correct? (p. 295)
Your answer: A polymerase constructs a new strand alongside each old one by pairing complementary nucleotides.
Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate, and each
functions as a template for the synthesis of a new complementary strand by means of DNA polymerase.
28. Correct In E. coli the error rate of DNA replication is approximately _____. (p. 299)
Your answer: 1per 1,000,000,000 nucleotides
Correct. This is a very high degree of accuracy.
29. Correct At each end of a DNA replication bubble is _____. (p. 295)
Your answer: a replication fork
Correct. Replication forks are found at the ends of replication bubbles.
30. Correct The DNA strand being produced continuously in the 5' --> 3' direction is called the _____ strand. (p. 296)
Your answer: leading
Correct. Building a new strand in this direction is simpler than building a new strand in the 3' --> 5' direction.
31. Correct After the formation of a replication bubble, which of the following is the correct sequence of enzyme use for the
synthesis of the lagging DNA strand? (p. 295)
Your answer: helicases, primase, DNA polymerase, ligase
Correct. First the double helix is unwound; primase makes the RNA primer; DNA polymerase elongates the growing strand
and replaces the RNA primer with DNA; and DNA ligase joins the Okazaki fragments.
32. Incorrect Unlike prokaryotic DNA replication, eukaryotic DNA replication _____. (p. 295)
Your answer: is completed by DNA polymerase
The correct answer: cannot be completed by DNA polymerase
No. Since prokaryotic DNA is circular, DNA polymerase can complete its replication.
33. Correct Telomeres _____. (p. 300)
Your answer: get shorter with continued cell division
Correct. However, the enzyme telomerase, which is not present in most cells of multicellular organisms, can lengthen the
telomeres.
34. Correct What is the correct order of the following DNA replication events at one point on a DNA molecule?
1.
2.
3.
4.
DNA unwinds as hydrogen bonds between the bases break.
Ligases solidify connections on the lagging strand.
Polymerases move along the leading strand, adding complementary nucleotides.
Polymerases proofread the strands.
(p. 295)
Your answer: 1,3,4,2
Correct. Helicases unwind the DNA; polymerase synthesizes the complementary strands, proofreading as it goes; ligase
joins the Okazaki fragments.
35. Correct During the replication of DNA molecules _____. (p. 293)
Your answer: both strands of a molecule act as templates
Correct. When a cell copies a DNA molecule, each strand serves as a template for ordering nucleotides into a new
complementary strand.
36. Correct The experiments of Meselson and Stahl showed that DNA _____. (p. 293)
Your answer: replicates in a semiconservative fashion
Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate, and each
functions as a template for the synthesis of a new complementary strand.
37. Correct The statement that each new molecule of DNA contains one parental and one newly synthesized strand of DNA
refers to _____. (p. 293)
Your answer: the semiconservative model of DNA replication
Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate, and each
functions as a template for the synthesis of a new, complementary strand.
38. Correct Two new strands of DNA molecules grow as bases are added by the enzyme _____. (p. 295)
Your answer: DNA polymerase
Correct. Elongation of new DNA at a replication fork is catalyzed by enzymes called DNA polymerases.
39. Correct The role of DNA polymerases in DNA replication is to _____. (p. 295)
Your answer: attach free nucleotides to the new strand
Correct. Elongation of new DNA at a replication fork is catalyzed by enzymes called DNA polymerases.
40. Correct What enzyme joins Okazaki fragments? (p. 297)
Your answer: DNA ligase
Correct. Helicases unwind the DNA; polymerase synthesizes the complementary strands, proofreading as it goes; ligase
joins the Okazaki fragments.
41. Correct Monomers for the synthesis of DNA are called _____. (p. 290)
Your answer: nucleotides
Correct. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate
group.
42. Correct Which of the following components is (are) required for DNA replication? (p. 297)
Your answer: RNA primer
Correct. In the cell, the preexisting chain, the primer, is RNA, not DNA.