Question 1

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?

Accepted Answer

A)  the 5' phosphate 
B)  C₆ 
C)  the 3' OH 
D)  a nitrogen from the nitrogen-containing base

Question 2

Which of the following lists represents the order of increasingly higher levels of organization of chromatin?

Accepted Answer

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

Question 3

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

Accepted Answer

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.

Question 4

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?

Accepted Answer

A)  DNA polymerase is an enzyme that synthesizes leading and lagging strands during replication only in one direction. 
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 should not be way longer than the distractors.

Question 5

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to radioactively label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Accepted Answer

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 16 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.

Question 6

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?

Accepted Answer

A)  protein 
B)  RNA 
C)  ribosome 
D)  DNA

Question 7

Use the figure to answer the following question.

Referring to the figure, what bases will be added to the primer as DNA replication proceeds?

Accepted Answer

A)  5′ C, A, G, C, A, G, A 3′ 
B)  3′ T, C, T, G, C, T, G 5′ 
C)  5′ A, G, A, C, G, A, C 3′ 
D)  3′ G, T, C, G, T, C, T 5′

Question 8

Which of the following types of cells are affected most by telomere shortening?

Accepted Answer

A)  only prokaryotic cells 
B)  only eukaryotic cells 
C)  cells in prokaryotes and eukaryotes 
D)  only animal cells

Question 9

The elongation of the leading strand during DNA synthesis

Accepted Answer

A)  progresses away from the replication fork. 
B)  occurs in the 3′ → 5′ direction. 
C)  produces Okazaki fragments. 
D)  depends on the action of DNA polymerase.

Question 10

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?

Accepted Answer

A)  sequence of bases 
B)  phosphate-sugar backbones 
C)  complementary pairing of bases 
D)  side groups of nitrogenous bases

Question 11

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?

Accepted Answer

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.

Question 12

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

Accepted Answer

A)  primase 
B)  DNA ligase 
C)  DNA polymerase III 
D)  helicase

Question 13

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

Accepted Answer

A)  DNA polymerase 
B)  DNA ligase 
C)  Okazaki fragments 
D)  primase

Question 14

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?

Accepted Answer

A)  Replication is semi-conservative. 
B)  Replication is not dispersive. 
C)  Replication is not conservative. 
D)  Replication is neither dispersive nor conservative.

Question 15

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?

Accepted Answer

A)  8% 
B)  16% 
C)  42% 
D)  58%

Question 16

In an analysis of the nucleotide composition of a molecule of DNA, which of the following combinations of base pairs will be found?

Accepted Answer

A)  A = C 
B)  A = G and C = T 
C)  A + C = G + T 
D)  G + C = T + A

Question 17

Which of the following statements accurately describes one characteristic of histones?

Accepted Answer

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.

Question 18

Which of the following investigators was (were) responsible for the discovery that in DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine?

Accepted Answer

A)  Alfred Hershey and Martha Chase 
B)  Oswald Avery, Maclyn McCarty, and Colin MacLeod 
C)  Erwin Chargaff 
D)  Matthew Meselson and Franklin Stahl

Question 19

In his transformation experiments, what phenomenon did Griffith observe?

Accepted Answer

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.

Question 20

Which of the following effects might be caused by reduced or very little active telomerase activity?

Accepted Answer

A)  Cells may become cancerous. 
B)  Telomere lengthens in germ cells. 
C)  Cells age and begin to lose function. 
D)  Cells maintain normal functioning.

Exam 16: The Molecular Basis of Inheritance