Bio Test 5

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53 terms · Quiz 16

During Griffith's experiments with Streptococcus pneumoniae in mice, material from _____ bacteria transformed _____ bacteria. ( Concept 16.1)

heat-killed nonvirulent ... living virulent
heat-killed virulent ... living nonvirulent
living nonvirulent ... heat-killed virulent
living virulent ... heat-killed nonvirulent
living nonvirulent ... living virulent

heat-killed virulent ... living nonvirulent

Correct. Griffith found that some of the living nonvirulent cells were converted to the virulent form.

Avery and his colleagues' 1944 experiment showed that DNA _____. ( Concept 16.1)

consists of sugars, phosphate groups, and bases
uses three bases to code for one amino acid
contains adenine, guanine, thymine, and cytosine
was the substance that transformed the bacteria in Griffith's experiment
has two strands held together with hydrogen bonds

was the substance that transformed the bacteria in Griffith's experiment
Correct. Avery and his colleagues announced that the transforming agent was DNA.

A scientist assembles 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 _____. ( Concept 16.1)

the protein and DNA of T4
a mixture of the DNA and proteins of both phages
the protein of T4 and the DNA of T2
the protein and DNA of T2
the protein of T2 and the DNA of T4

the protein and DNA of T4
Correct. The protein and DNA would match that of the phage whose DNA was used.

In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that _____. ( Concept 16.1)

bacteriophages can infect bacteria
genes are on chromosomes
the genetic material of the phage is DNA
the genetic material of the phage is protein
DNA is made of nucleotides

the genetic material of the phage is DNA
Correct. In order to replicate, viral material must enter a bacterial cell. This experiment showed that the viral DNA had entered the bacterial cell.

Up until Hershey and Chase showed that DNA was the genetic molecule, what molecule was considered the best candidate for carrying genetic information and why? ( Concept 16.1)

proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed
carbohydrates because they are found in abundance in all organisms
amino acids because of all the ways they can join together
sterols because of the different variations on their ring structure
nucleoside triphosphates because of the ability to add and remove phosphate groups

proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed
Many scientists believed that proteins must be the chemical carriers of genetic information.

Monomers for the synthesis of DNA are called _____. ( Concept 16.1)

disaccharides
nucleotides
monosaccharides
fatty acids
amino acids

nucleotides
Correct. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate group.

Chargaff found that for DNA _____. ( Concept 16.1)

the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
A + T = 50% of the total bases
the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1
A + T = G + C

the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1

What technique was most helpful to Watson and Crick in developing their model for the structure of DNA? ( Concept 16.1)

X-ray crystallography
radioactive labeling
transgenic animals
cloned DNA
electrophoresis

X-ray crystallography
Correct. Watson and Crick based their model of DNA on insights they were able to gain from Franklin's X-ray diffraction photo.

In DNA, the two purines are _____, and the two pyrimidines are _____. ( Concept 16.1)

adenine and thymine ... cytosine and guanine
adenine and cytosine ... guanine and thymine
cytosine and guanine ... adenine and thymine
cytosine and thymine ... adenine and guanine
adenine and guanine ... cytosine and thymine

adenine and guanine ... cytosine and thymine

Correct. Purines have two rings, and pyrimidines have one.

Which of the following is correct? ( Concept 16.1)

Adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine.
Adenine forms three covalent bonds with thymine; guanine forms two covalent bonds with cytosine.
Adenine forms two covalent bonds with thymine; guanine forms three covalent bonds with cytosine.
Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine.
Adenine forms three hydrogen bonds with thymine; guanine forms two hydrogen bonds with cytosine.

Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine.
Correct. This is a consequence of the characteristics of the bases.

The two sugar-phosphate strands that form the rungs of a DNA double helix are joined to each other through _____. ( Concept 16.1)

5' deoxyribose and phosphate bonds
covalent bonds between nitrogen atoms in adenine and in thymine
covalent bonds between carbon atoms in deoxyribose molecules
ionic bonds between guanine and cytosine
hydrogen bonds between nucleotide bases

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.

The information in DNA is contained in _____. ( Concept 16.1)

the sequence of nucleotides along the length of the two strands of the DNA molecule
the types of sugars used in making the DNA molecule
the variation in the structure of nucleotides that make up the DNA molecule
the sequence of amino acids that makes up the DNA molecule
All of the listed responses are correct.

the sequence of nucleotides along the length of the two strands 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.

Who is credited with explaining the structure of the DNA double helix? ( Concept 16.1)

Jacob and Monod
Avery, McCarty, and MacLeod
Watson and Crick
Hershey and Chase
Griffith

Watson and Crick
Correct. In April 1953, Watson and Crick published a one-page paper in the journal Nature elucidating their molecular model for the DNA double helix.

Which of the following attributes of DNA is most crucial to its accurate duplication? ( Concept 16.2)

its specific sequence of bases
its helical nature and hydrogen bonding
its deoxyribose sugar and phosphate groups
its phosphodiester linkages and complementary strands
its specific base pairing and hydrogen bonding

its specific base pairing and hydrogen bonding
Correct. The hydrogen bonding makes it easy to separate the two strands. Specific complementary base pairing ensures that an accurate strand will be constructed on each template strand.

During the replication of DNA, _____. ( Concept 16.2)

errors never occur
the cell undergoes mitosis
both strands of a molecule act as templates
the reaction is catalyzed by RNA polymerase
only one strand of the molecule acts as a template

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.

The experiments of Meselson and Stahl showed that DNA _____. ( Concept 16.2)

is the genetic material
codes for the sequence of amino acids in proteins
contains complementary base pairing
is composed of nucleotides
replicates in a semiconservative fashion

replicates in a semiconservative fashion
Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate. Each functions as a template for the synthesis of a new complementary strand.

The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that _____. ( Concept 16.2)

the DNA is packaged into several linear chromosomes
most of the DNA is in the form of plasmids
both have a single circular chromosome
histones are present in the nucleosomes
both have a sugar-phosphate backbone

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.

Which of the following statements about replication origins is correct? ( Concept 16.2)

In bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin.
The two strands of DNA at the origin are separated, allowing the formation of a replication bubble.
In both prokaryotes and eukaryotes, replication proceeds in both directions from each origin.
Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins.
All of the listed responses are correct.

All of the listed responses are correct.

At each end of a DNA replication bubble is _____. ( Concept 16.2)

a telomere
a gene
a replication fork
a ribosome
an origin of replication

a replication fork

Correct. Replication forks are found at the ends of replication bubbles.

The role of DNA polymerases in DNA replication is to _____. ( Concept 16.2)

link together short strands of DNA
attach free nucleotides to the new DNA strand
synthesize an RNA primer to initiate DNA strand synthesis
separate the two strands of DNA
All of the listed responses are correct.

attach free nucleotides to the new DNA strand
Elongation of new DNA at a replication fork is catalyzed by enzymes called DNA polymerases.

The rate of elongation in prokaryotes is _____ the rate in eukaryotes. ( Concept 16.2)

much faster than
The rates are not comparable, because elongation only occurs in prokaryotes.
about the same speed as
much slower than
sometimes faster and sometimes slower than

much faster than

Correct. The rate of elongation is about 500 nucleotides per second in bacteria and about 50 nucleotides per second in human cells.

The two strands of a DNA double helix are antiparallel. This means that _____. ( Concept 16.2)

the two strands are mirror images
only one of the two strands can be used as a template for replication, because DNA polymerase only works in one direction
one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction
they both run in the 3' to 5' direction
one strand is actually composed of RNA

one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction

Correct. This allows the two strands to fit together properly.

One strand of a DNA molecule has the base sequence 5′-ATAGGT-3′. The complementary base sequence on the other strand of DNA will be 3′-_____-5′. ( Concept 16.2)

TGGATA
TATCCA
UAUCCA
ATAGGT
TGGAUA

TATCCA

Correct. A always pairs with T, and G with C.

DNA polymerase adds nucleotides to the _____ of the leading strands, and to the _____ of the lagging strands (Okazaki fragments). ( Concept 16.2)

5′ end ... 3′ end
sugar group ... phosphate group
3′ end ... 3′ end
3′ end ... 5′ end
5′ end ... 5′ end

3′ end ... 3′ end

Correct. Although the leading strand and lagging strand are synthesized in opposing directions with respect to the movement of the replication fork, the DNA polymerase enzyme can only add nucleotides to the 3′ end of a growing DNA strand.

What enzyme joins Okazaki fragments? ( Concept 16.2)

DNA polymerase
DNA ligase
helicase
topoisomerase
primase

DNA ligase
Correct. Helicases unwind the DNA; polymerase synthesizes the complementary strands; ligase joins the Okazaki fragments.

After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand? ( Concept 16.2)

helicases, primase, DNA polymerases, ligase
helicases, primase, ligase, DNA polymerases
primase, helicases, DNA polymerases, ligase
ligase, primase, DNA polymerases, helicases
helicases, DNA polymerases, primase, ligase

helicases, primase, DNA polymerases, ligase
Correct. First the double helix is unwound; primase makes the RNA primer; DNA polymerases elongate the growing strand and replace the RNA primer with DNA; and DNA ligase joins the Okazaki fragments.

Which of the following components is required for DNA replication? ( Concept 16.2)

proteases
sucrases
ribosomes
transfer RNA
RNA primer

RNA primer

Correct. In the cell, the preexisting chain, the primer needed to initiate DNA elongation, is RNA, not DNA.

The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by _____. ( Concept 16.2)

nuclease
primase
DNA polymerase I
DNA polymerase III
ligase

DNA polymerase I

Correct. Upon encountering the RNA primer, DNA polymerase III falls off the DNA and is replaced by DNA polymerase I.

The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called _____. ( Concept 16.2)

relievase
primase
ribosomes
topoisomerase
ligase

topoisomerase

Correct. Topoisomerase cuts the DNA and allows it to spin around its central axis, which relieves the strain caused by twisting.

Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix? ( Concept 16.2)

One of the strands is rapidly degraded, preventing the double helix from re-forming.
The helicase pushes the two strands so far apart that they have no chance of finding each other.
DNA polymerase follows the helicase so closely that there is no chance for the strands to come back together.
Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.
The helicase modifies the DNA in such a way as to eliminate the affinity between the two strands.

Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.

Correct. As soon as the helicase passes, the single-strand binding proteins rapidly coat the unwound DNA and prevent the strands from coming back together.

Which description of DNA replication is correct? ( Concept 16.2)

Ligase assembles single-stranded codons, then polymerase knits these codons together into a DNA strand.
The two strands of DNA separate, and restriction enzymes cut up one strand. Then, the DNA polymerase synthesizes two new strands out of the old ones.
Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates.
The two strands separate, and each one receives a complementary strand of RNA. Then this RNA serves as a template for the assembly of many new strands of DNA.
Ligase separates the two strands of the DNA double helix. Then, DNA polymerase synthesizes the leading strand and primase synthesizes the lagging strand.

Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates.

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.

In what way(s) is our traditional representation of DNA polymerase molecules moving like locomotives along a track inaccurate? ( Concept 16.2)

The proteins involved in replication do not move; instead, DNA is drawn through the complex.
DNA polymerase acts as part of a large complex of proteins, not like a single locomotive.
Like a train on a track, DNA polymerase must add nucleotides sequentially. It cannot jump around.
Both the first and second answers are correct.
DNA polymerase completes replication of one strand and then begins the other.

Both the first and second answers are correct.

Correct. DNA polymerase is part of a replication machine that may be anchored to the nuclear matrix. DNA is drawn into the complex, and the newly synthesized strands are extruded.

The overall error rate in the completed DNA molecule is approximately _____. ( Concept 16.2)

1 error per 1,000,000,000 nucleotides
1 error per 1,000,000 nucleotides
1 error per 10,000,000,000 nucleotides
1 error per 1,000 nucleotides
1 error per 100 nucleotides

1 error per 10,000,000,000 nucleotides
Correct. The rate of initial pairing errors during replication is about 1 in 100,000. This level of accuracy is then dramatically enhanced by the different proofreading mechanisms discussed in the chapter.

The incorporation of an incorrect base into the DNA during replication _____. ( Concept 16.2)

is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur
will almost certainly lead to the death of the cell
can be repaired by the mismatch repair system
will trigger the cell to destroy the new strand, and replication will begin again
cannot be repaired, and a new mutation will invariably result

can be repaired by the mismatch repair system

Correct. The mismatch repair system can detect and rectify incorrectly incorporated bases.

Which set of enzymes is involved in nucleotide excision repair? ( Concept 16.2)

hydrolase, nuclease, and ligase
DNA polymerase, helicase, primase
nuclease, DNA polymerase, primase
ligase, nuclease, and primase
nuclease, DNA polymerase, and ligase

nuclease, DNA polymerase, and ligase

Correct. Nucleotide excision repair involves nucleases, DNA polymerase, and ligase.

Individuals with the disorder xeroderma pigmentosum _____. ( Concept 16.2)

have difficulty repairing thymine dimers
often have inherited defects in the nucleotide excision repair system
have high rates of skin cancer
are hypersensitive to sunlight
All of the listed responses are correct.

All of the listed responses are correct.

Correct. Individuals with this disorder are unusually sensitive to sunlight because they cannot repair the thymine dimers that can result from exposure to ultraviolet light.

Unlike prokaryotic DNA replication, replication of eukaryotic chromosomes _____. ( Concept 16.2)

cannot be completed by DNA polymerase
has a single origin
is semiconservative
involves two leading strands and no lagging strands
is error free

cannot be completed by DNA polymerase

Correct. This is the case because eukaryotic chromosomes are linear, and DNA polymerase cannot replicate the extreme 3' end of the template strands.

Telomeres _____. ( Concept 16.2)

get shorter with continued cell division
are shorter for younger individuals
remain the same regardless of the frequency of cell division
are found in both prokaryotic and eukaryotic cells
get longer with continued cell division

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.

Telomerase _____. ( Concept 16.2)

is an enzyme that lengthens telomeres
slows the rate of cancer cell growth
splits telomeres
speeds cell aging
prevents the loss of centromeric DNA

is an enzyme that lengthens telomeres

Correct. Telomerase is an enzyme made of a protein and an RNA sequence that serves as a template for adding additional telomeric DNA sequences. Telomerase is found in germ cells and in many human cancers, increasing the longevity of these cells.

Which of the following best illustrates the importance of altered DNA nucleotides in evolutionary processes?( Concept 16.2)

In a temporally variable environment, a population of bacteria with an elevated rate in replication error can have a selective advantage over other populations with lower rates in replication error.
Natural selection will always select to reduce rates of replication errors within populations.
A population of bacteria with an elevated rate of replication error is always eliminated by natural selection.
In a temporally stable environment, a population of bacteria with an elevated rate in replication error has a selective advantage over other species with reduced rates in replication error.
A population of bacteria with a very low rate of replication error always has an evolutionary advantage over other populations with higher rates.

In a temporally variable environment, a population of bacteria with an elevated rate in replication error can have a selective advantage over other populations with lower rates in replication error.
Correct. In an environment that undergoes rapid change over time, an elevated rate of mutations due to uncorrected errors in replication can be advantageous if such errors generate greater phenotypic variation in the population and thus greater likelihood that some individuals in the population will be well matched to the prevailing environmental conditions.

In a comparison between asexually reproducing bacteria and sexually reproducing multicellular eukaryotes, uncorrected errors in replication are more likely to be transmitted to subsequent generations in bacteria than in multicellular eukaryotes. Which of the following provides the best evidence-based explanation for this difference?( Concept 16.2)

Although the genome for each is represented as pairs of homologous chromosomes, errors in bacteria affect both homologs, but only one is affected in eukaryotes.
Unlike multicellular eukaryotes, bacteria lack DNA repair enzymes, so there are just more uncorrected errors at play.
Being asexual and single-celled, all uncorrected errors of replication in bacteria are transmitted to subsequent generations. Multicellular eukaryotes typically reproduce sexually, so uncorrected errors are transmitted only if they occur in germ cells that meiotically divide to produce gametes.
Only errors that lead to faster growing strains are left uncorrected in bacteria, whereas all errors are detected and repaired in multicellular eukaryotes.
The third and fourth listed responses can explain this phenomenon.

Being asexual and single-celled, all uncorrected errors of replication in bacteria are transmitted to subsequent generations. Multicellular eukaryotes typically reproduce sexually, so uncorrected errors are transmitted only if they occur in germ cells that meiotically divide to produce gametes.

Correct. Uncorrected errors in dividing somatic cells of multicellular eukaryotes may lead to problems in individuals, but they will not be transmitted to offspring. In bacteria, however, all uncorrected errors are transmitted to subsequent generations because cell division equates to reproduction in single-celled organisms.

What is the major difference between bacterial chromosomes and eukaryotic chromosomes? ( Concept 16.3)

Bacterial chromosomes have much more protein associated with the DNA than eukaryotes.
There is no difference between bacterial and eukaryotic chromosomes.
Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes.
The DNA of bacterial chromosomes has a slightly different structure.
Eukaryotes have a single circular chromosome whereas bacteria have several linear chromosomes.

Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes.

Correct. The arrangement of DNA and its association with proteins is different for prokaryotes and eukaryotes.

Put the following DNA-containing entities in order according to the amount of DNA found in their genomes. ( Concept 16.3)

bacteria, virus, eukaryote
eukaryote, virus, bacteria
virus, bacteria, eukaryote
bacteria, eukaryote, virus
They all have about the same amount of DNA.

virus, bacteria, eukaryote

Correct. In general, viruses have the smallest genomes, followed by bacteria, with eukaryotes having the largest genomes.

Why were many of the early experiments on DNA carried out on viruses and bacteria? ( Concept 16.3)

They have short generation times.
They can interact with each other.
They have relatively small genomes.
Their chromosomes have a simpler structure.
All of the responses are true.

All of the responses are true.
Correct. Experiments on DNA were, and still are, carried out on these subjects for all of these reasons.

The "beads on a string" seen in interphase chromatin are _____. ( Concept 16.3)

looped domains
heterochromatin
histone tails
nucleoids
nucleosomes

nucleosomes
Correct. Nucleosomes are complexes of DNA wrapped around eight histone molecules.

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

the polysaccharide coat of bacteria caused pneumonia.
the protein coat from pathogenic cells was able to transform nonpathogenic cells.
some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
bacteriophages injected DNA into bacteria.
heat-killed pathogenic cells caused pneumonia.

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

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

Polymerase can work on only one strand at a time.
DNA ligase works only in the 39 S59 direction.
The origins of replication occur only at the 59 end.
DNA polymerase can join new nucleotides only to the 39 end of a growing strand.
Helicases and single-strand binding proteins work at the 59 end.

DNA polymerase can join new nucleotides only to the 39 end of a growing strand.

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

G = T
A = G
A + T = G + T
A = C
A + G = C + T

A + G = C +

The elongation of the leading strand during DNA synthesis

progresses away from the replication fork.
produces Okazaki fragments.
occurs in the 39 S59 direction.
does not require a template strand.
depends on the action of DNA polymerase.

depends on the action of DNA polymerase.

In a nucleosome, the DNA is wrapped around

histones.
a thymine dimer.
ribosomes.
polymerase molecules.
satellite DNA.

histones.

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 high-density and one low-density band
one high-density and one intermediate-density band
one intermediate-density band
one low-density band
one low-density and one intermediate-density band

:

one low-density and one intermediate-density band

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?

nucleotides
Okazaki fragments
DNA polymerase
DNA ligase
primase

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?

telomerase, primase, DNA polymerase
nuclease, telomerase, primase
telomerase, helicase, single-strand binding protein
DNA ligase, replication fork proteins, adenylyl cyclase
nuclease, DNA polymerase, DNA ligase

:

nuclease, DNA polymerase, DNA ligase

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