Chapter 16 and 19 Mastering Biology

Which of the following events stimulates the production of viral particles in a host cell?

Activation of the host cell by cytokines, growth factors, or antigens.

What materials does DNA polymerase require in order to synthesize a complete strand of DNA?

All four deoxyribonucleotides triphosphates (containing A, C, T, or G) 3'-OH end of the new DNA strand Single-stranded DNA template

Which of the following statements accurately describes the differences between DNA replication in prokaryotes and DNA replication in eukaryotes?

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

Early, flawed DNA models proposed by Watson and Crick and by Linus Pauling correctly described which property of DNA?

DNA is composed of sugars, phosphates, and bases.

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?

DNA polymerase

What catalyzes DNA synthesis?

DNA polymerase

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

DNA polymerase III

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

DNA polymerase can assemble DNA only in the 5' to 3' direction

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

In the early 1950s, many researchers were racing to describe the structure of DNA using different approaches. Which of the following statements is true?

Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data.

In his transformation experiments, what phenomenon 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.

In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding? See Concept 16.1 (Page)

Radioactively labeled phosphorus was present inside the infected bacteria

In E. coli replication the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following would you expect?

Replication would not occur on either the leading or lagging strand.

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?

Telomerase eliminates telomere shortening and retards aging.

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

The cell's DNA could not be packed into its nucleus.

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication?

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.

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. What would you expect to happen to the plants that were sprayed with the mixture?

The plants would develop the typical symptoms of TMV infection.

Hershey and Chase used a DNA-based virus for their work. What would the results have been if they had used an RNA virus?

With an RNA virus radioactive RNA would have been in the final pellet.

Evidence suggests that factors which contribute towards the virulence of E. coli strain O157:H7, a bacterial strain reported to cause several food poisoning deaths, are caused by genes from a virus that infects bacteria. Considering this evidence, which statement most likely explains how the O157:H7 population acquired the genetic variation that distinguishes the strain from harmless E. coli strains, such as those that reside in our intestines?

The virus infected the bacterium, and allowed the bacterial population to replicate with a copy of the phage genome in each new bacterium.

A hydroxyl is present at the 3' end of the growing DNA strand. What is at the 5' end?

a phosphate group

Short segments of newly synthesized DNA are joined into a continuous strand by _____.

ligase

Cycle A is the _____ cycle and cycle B is the _____ cycle.

lytic ... lysogenic

The pointer is indicating the virus's _____.

genome

What is the function of the enzyme topoisomerase in DNA replication?

relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

The action of helicase creates _____.

replication forks and replication bubbles

The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?

the lytic cycle only

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.

thymine ... cytosine

In E. coli, what is the function of DNA polymerase III?

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

Viral DNA makes mRNA by the process of _____.

transcription

What did Rosalind Franklin's famous photo 51 show?

DNA is a helix.

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%

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

5 A, G, A, C, G, A, C 3

At a specific area of a chromosome, the sequence of nucleotides below 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'

Given a template strand of 3'-ATGCTTGGACA-5' and a partially-made complementary strand containing only 5'-TAC-3', what would be the sequence of the new strand of DNA (including the 5'-TAC-3') if the only additional nucleotides available to DNA polymerase were those containing the bases G, A, and C?

5'-TACGAACC-3'

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

A + C = G + T

Which of the following characteristics is typical of the lytic cycle of a bacteriophage?

A large number of phages are released at a time.

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

What did the structure of DNA's double helix suggest about DNA's properties?

DNA can change. Errors in copying can result in changes in the DNA sequence that could be inherited by future generations. DNA stores genetic information in the sequence of its bases. DNA can be replicated by making complementary copies of each strand.

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?

DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication.

What is the role of DNA polymerase during DNA synthesis?

DNA polymerase is the enzyme that catalyzes the addition of a nucleotide onto the 3' end of a growing DNA strand.

During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?

DNA synthesis can take place only in the 5' to 3' direction.

Which of the following statements describes the process of transformation in bacteria?

External DNA is taken into a cell, becoming part of the cell's genome.

True or false? The human immunodeficiency virus (HIV) uses reverse transcriptase to make double-stranded RNA copies of its DNA genome.

False

In the 1950s, when Watson and Crick were working on their model of DNA. which concepts were well accepted by the scientific community?

Genes are located on chromosomes .Chromosomes are made up of protein and nucleic acid. Chromosomes are found in the nucleus.

How does HIV cause disease?

HIV kills cells that defend the body against disease.

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

Heterochromatin is highly condensed, whereas euchromatin is less compact.

Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?

High mutation rate due to lack of proofreading of RNA genome replication errors.

Which of the following molecular characteristics cause histones to bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infectious agent.I. Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious.II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope.III. Culture the substance on nutritive medium, away from any plant cells.IV. Treat the sample with proteases that digest all proteins, and then determine whether the substance is still infectious.If you already know that the infectious agent was either a virus or a prion, which method(s) listed above would allow you to distinguish between these two possibilities?

I only

You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infectious agent.I. Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious.II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope.III. Culture the substance on nutritive medium, away from any plant cells.IV. Treat the sample with proteases that digest all proteins, and then determine whether the substance is still infectious.If you already know that the infectious agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities?

II or III

Which enzyme inserts viral DNA into the host's chromosomal DNA?

Integrase

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

It joins Okazaki fragments together.

Which replicative cycle describes a virus that can integrate its genome into the host cell's genome?

Lysogenic

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

No replication fork will be formed.

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

Phosphate groups

Which of the following enzymes creates a primer for DNA polymerase?

Primase

Which of the following statements about DNA synthesis is true?

Primers are short sequences that allow the initiation of DNA synthesis.

In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation, "swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus, sequences from bird, pig, and human viruses were all found within this newly identified virus. What is the most likely explanation of why this virus contained sequences from bird, pig, and human viruses?

Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.

Addition of a nucleotide onto a DNA strand is an endergonic reaction. What provides the energy to drive the reaction?

Release of pyrophosphate from the incoming nucleotide, and then hydrolysis of the pyrophosphate to inorganic phosphate

Why do RNA viruses appear to have higher rates of mutation?

Replication of their genomes does not involve proofreading.

Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5 end, the RNA genome has a viral protein (VPg) instead of a 5 cap. This is followed by a non-translated leader sequence, and then a single long protein-coding region (~7,000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acids similar in structure to those that are found in viruses and other organisms. Short-period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides What conclusion is most consistent with the results of the radioactive labeling experiment?

The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.

Erwin Chargaff observed that the proportions of adenine (A) and thymine (T) bases were always equal, as were the proportion of guanine (G) and cytosine (C). Chargaff's observation suggests which of the following statements?

The data suggest that A would always pair with T and G would always pair with C in a DNA molecule.

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, and mutations to the DNA in their skin cells are left uncorrected. Why are the mutations not corrected in individuals with this disorder?

The disorder causes cells to be unable to repair thymine dimers.

Which of the following statements accurately describes the lysogenic cycle of lambda (λ) phage?

The phage genome is integrated in the host chromosome where it is replicated along with the host genome.

How does HIV bind to a host cell?

The viral envelope proteins interact with CD4 and a co-receptor on the cell membrane.

Viruses use the host cell's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

The viral genome codes for specialized enzymes not found in the host cells.

Which of the following statements about Okazaki fragments in E. coli is true?

They are formed on the lagging strand of DNA.

How do enveloped viruses differ from nonenveloped viruses?

They have a membrane-like outer covering.

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

Topoisomerase

True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.

True

Which of the following statements correctly describes a difference between viruses and prions?

Viruses generally cause disease symptoms quickly, whereas prions generally take many years to cause disease symptoms.

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 (a lighter isotope). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

d

After DNA replication is completed, _____.

each new DNA double helix consists of one old DNA strand and one new DNA strand

In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?

no mediator is required; the new viruses self-assemble

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

only eukaryotic cells

Which of the following types of viral genomes could be transcribed using reverse transcriptase?

ssRNA

What are the chemical components of a DNA molecule?

sugars phosphate groups nitrogenous bases

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

template

In the lysogenic cycle _____.

viral DNA is replicated along with host DNA