Chapter 13

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

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

5'-A C G U U A G G-3'

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?

8%

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

A + G = C + T

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?

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

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?

Descendants of the living cells are also phosphorescent.

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

Erwin Chargaff

Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme?

GGCC CCGG

Which of the following statements correctly describes chromatin?

Heterochromatin is highly condensed, whereas euchromatin is less compact.

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

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

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

Which of the following statements best describes the eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together.

In his transformation experiments, what did Griffith observe?

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

Which of the following statements describes one difference between DNA replication in prokaryotes and DNA replication in eukaryotes?

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

What is meant by the description "antiparallel" regarding the two strands of nucleic acids that make up DNA?

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

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

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

Analysis of the data obtained shows that two students each have two fragments, two students each have three fragments, and two students each have one only. What does this demonstrate?

The two students who have two fragments have one restriction site in this region.

) Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?

They cannot repair thymine dimers.

How is transformation in bacteria most accurately described?

assimilation of external DNA into a cell

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase.

Which of the following sets of materials is required by both eukaryotes and prokaryotes for DNA replication?

double-stranded DNA, four kinds of DNA nucleotides, primers, origins of replication

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

eading strands and Okazaki fragments.

During DNA replication, which of the following enzymes separates the DNA strands during replication?

helicase

In a nucleosome, the DNA is wrapped around

histones

Which of the following modifications is most likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?

increasing the length of the DNA fragment

During DNA replication, which of the following enzymes covalently connects segments of DNA?

ligase

In which order do the necessary enzymes act to repair a thymine dimer by nucleotide excision repair?

nuclease, DNA polymerase, DNA ligase

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?

nuclease, DNA polymerase, DNA ligase

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

nucleosome, 30-nm chromatin fiber, looped domain

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?

one low-density and one intermediate-density band

Which of the following enzymes synthesizes short segments of RNA?

primase

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

single-strand binding proteins

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

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

the 30-nm chromatin fiber

Given the damage caused by UV radiation, the kind of gene affected in those with xeroderma pigmentosum is one whose product is involved with

the ability to excise damage to single-stranded DNA and replace it.

The leading and the lagging strands of DNA formed during DNA replication differ in that

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

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information based on which of the following characteristics?

the sequence of bases

What is the function of DNA polymerase III?

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

Why might they be conducting such an experiment?

to find which of the students has which alleles

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

DNA contains phosphorus, whereas protein does not.

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. After adding 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 the student probably left out of the mixture?

DNA ligase

During DNA replication, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

DNA polymerase I

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

DNA polymerase III

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

DNA polymerase can join new nucleotides only to the 3' end of a preexisting strand.

A new DNA strand elongates only in the 5' to 3' direction because

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