Question 1

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 2

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 3

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 4

In his work with pneumonia-causing bacteria and mice, Griffith found that

Accepted Answer

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.

Question 5

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 6

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?

Accepted Answer

A)  primase 
B)  ligase 
C)  DNA polymerase 
D)  single-strand DNA binding proteins

Question 7

Which of the following statements accurately describes the structure of a eukaryotic chromosome?

Accepted Answer

A)  It is composed of a single strand of DNA. 
B)  It is constructed as a series of nucleosomes wrapped around two DNA molecules. 
C)  It has different numbers of genes in different cell types of an organism. 
D)  It is a single linear molecule of double-stranded DNA plus proteins.

Question 8

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

Accepted Answer

A)  The origins of replication occur only at the 5′ end. 
B)  Helicases and single-strand binding proteins work at the 5′ end. 
C)  DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel. 
D)  DNA ligase works only in the 3′ → 5′ direction.

Question 9

A heat-killed, phosphorescent (light-emitting)strain of bacteria is mixed with a living, non-phosphorescent strain. Further observations of the mixture show that some of the living cells are now phosphorescent. Which of the following observations would provide the best evidence that the ability to phosphoresce is a heritable trait?

Accepted Answer

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

Question 10

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

Accepted Answer

A)  nuclease, DNA polymerase, DNA ligase 
B)  telomerase, primase, DNA polymerase 
C)  telomerase, helicase, single-strand binding protein 
D)  DNA ligase, replication fork proteins, adenylyl cyclase

Question 11

Researchers found a strain of E. coli bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these results?

Accepted Answer

A)  The single-strand binding proteins were malfunctioning during DNA replication. 
B)  There were one or more base pair 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 3′ end of the growing nucleic acid chain.

Question 12

Which of the following statements correctly describes the structure of chromatin?

Accepted Answer

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.

Question 13

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 14

Why does a new DNA strand elongate only in the 5' to 3' direction during DNA replication?

Accepted Answer

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.

Question 15

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 during DNA replication?

Accepted Answer

A)  ribozymes 
B)  DNA polymerase 
C)  ATP 
D)  RNA primers

Question 16

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 17

Thymine makes up 28% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be guanine?

Accepted Answer

A)  8% 
B)  16% 
C)  22% 
D)  72%

Question 18

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 19

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine. What is the significance of the structural arrangement?

Accepted Answer

A)  It allows variable width of the double helix. 
B)  It permits complementary base pairing. 
C)  It determines the tertiary structure of a DNA molecule. 
D)  It determines the type of protein produced.

Question 20

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). Which two classes of DNA do these different samples represent?

Accepted Answer

A)  leading strands and Okazaki fragments 
B)  lagging strands and Okazaki fragments 
C)  Okazaki fragments and RNA primers 
D)  leading strands and RNA primers

Exam 16: The Molecular Basis of Inheritance