Chapter 16 DNA replication

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase.

In a nucleosome, the DNA is wrapped around

histones

The overall error rate in the completed DNA molecule is approximately _____. a) 1 error per 10,000,000,000 nucleotides b) 1 error per 100 nucleotides c) 1 error per 1,000,000 nucleotides d) 1 error per 1,000 nucleotides e) 1 error per 1,000,000,000 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.

DNA polymerase adds nucleotides to the _____ of the leading strands, and to the _____ of the lagging strands (Okazaki fragments). a) 3′ end ... 5′ end b) 5′ end ... 5′ end c) sugar group ... phosphate group d) 3′ end ... 3′ end e) 5′ end ... 3′ 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.

Which of the following is correct? a) Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine. b) Adenine forms two covalent bonds with thymine; guanine forms three covalent bonds with cytosine. c) Adenine forms three covalent bonds with thymine; guanine forms two covalent bonds with cytosine. d) Adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine. e) 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.

Individuals with the disorder xeroderma pigmentosum _____. a) have difficulty repairing thymine dimers b) often have inherited defects in the nucleotide excision repair system c) are hypersensitive to sunlight d) have high rates of skin cancer e) 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.

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

All of the listed responses are correct.

Why were many of the early experiments on DNA carried out on viruses and bacteria? a) They have relatively small genomes. b) They can interact with each other. c) They have short generation times. d) Their chromosomes have a simpler structure. e) All of the responses are true.

All of the responses are true

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

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

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? a) 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. b) Unlike multicellular eukaryotes, bacteria lack DNA repair enzymes, so there are just more uncorrected errors at play. c) 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. d) Only errors that lead to faster growing strains are left uncorrected in bacteria, whereas all errors are detected and repaired in multicellular eukaryotes. e) 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.

In what way(s) is our traditional representation of DNA polymerase molecules moving like locomotives along a track inaccurate a) The proteins involved in replication do not move; instead, DNA is drawn through the complex. b) DNA polymerase acts as part of a large complex of proteins, not like a single locomotive. c) Like a train on a track, DNA polymerase must add nucleotides sequentially. It cannot jump around. d) Both the first and second answers are correct. e) DNA polymerase completes replication of one strand and then begins the other.

Both the first and second answers are correct

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?

DNA ligase

What enzyme joins Okazaki fragments? a) helicase b) DNA polymerase c) DNA ligase d) topoisomerase e) primase

DNA ligase

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 _____. a) ligase b) DNA polymerase I c) nuclease d) DNA polymerase III e) primase

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

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 growing strand

Which description of DNA replication is correct? a) Ligase assembles single-stranded codons, then polymerase knits these codons together into a DNA strand. b) 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. c) 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. d) Ligase separates the two strands of the DNA double helix. Then, DNA polymerase synthesizes the leading strand and primase synthesizes the lagging strand. e) 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.

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.

Which of the following best illustrates the importance of altered DNA nucleotides in evolutionary processes? a) 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. b) A population of bacteria with a very low rate of replication error always has an evolutionary advantage over other populations with higher rates. c) 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. d) Natural selection will always select to reduce rates of replication errors within populations. e) A population of bacteria with an elevated rate of replication error is always eliminated by natural selection.

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.

Which of the following components is required for DNA replication? a) sucrases b) proteases c) RNA primer d) ribosomes e) transfer RNA

RNA primer

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? a) DNA polymerase follows the helicase so closely that there is no chance for the strands to come back together. b) The helicase pushes the two strands so far apart that they have no chance of finding each other. c) One of the strands is rapidly degraded, preventing the double helix from re-forming. d) Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming. e) 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.

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′. a) ATAGGT b) TGGATA c) UAUCCA d) TGGAUA e) TATCCA

TATCCA

Who is credited with explaining the structure of the DNA double helix? a) Avery, McCarty, and MacLeod b) Hershey and Chase c) Jacob and Monod d) Griffith e) Watson and Crick

Watson and Crick

At each end of a DNA replication bubble is _________ a) a telomere b) an origin of replication c) a ribosome d) a gene e) a replication fork

a replication fork

In DNA, the two purines are _____, and the two pyrimidines are _____ a) adenine and cytosine ... guanine and thymine b) cytosine and thymine ... adenine and guanine c) adenine and guanine ... cytosine and thymine d) cytosine and guanine ... adenine and thymine e) adenine and thymine ... cytosine and guanine

adenine and guanine ... cytosine and thymine

The role of DNA polymerases in DNA replication is to _____ a) synthesize an RNA primer to initiate DNA strand synthesis b) link together short strands of DNA c) separate the two strands of DNA d) attach free nucleotides to the new DNA strand e) All of the listed responses are correct.

attach free nucleotides to the new DNA strand

The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that _____. a) histones are present in the nucleosomes b) most of the DNA is in the form of plasmids c) both have a single circular chromosome d) the DNA is packaged into several linear chromosomes e) both have a sugar-phosphate backbone

both have a sugar-phosphate backbone

During the replication of DNA, _____. a) only one strand of the molecule acts as a template b) the cell undergoes mitosis c) errors never occur d) the reaction is catalyzed by RNA polymerase e) both strands of a molecule act as templates

both strands of a molecule act as templates

The incorporation of an incorrect base into the DNA during replication _____. a) will almost certainly lead to the death of the cell b) can be repaired by the mismatch repair system c) is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur d) cannot be repaired, and a new mutation will invariably result e) will trigger the cell to destroy the new strand, and replication will begin again

can be repaired by the mismatch repair system

Unlike prokaryotic DNA replication, replication of eukaryotic chromosomes _____. a) has a single origin b) is error free c) is semiconservative d) cannot be completed by DNA polymerase e) involves two leading strands and no lagging strands

cannot be completed by DNA polymerase Explanation: Both prokaryotic and eukaryotic DNA replication are semiconservative.

Telomeres _____. a) get shorter with continued cell division b) get longer with continued cell division c) remain the same regardless of the frequency of cell division d) are found in both prokaryotic and eukaryotic cells e) are shorter for younger individuals

get shorter with continued cell division

During Griffith's experiments with Streptococcus pneumoniae in mice, material from _____ bacteria transformed _____ bacteria. a) heat-killed nonvirulent ... living virulent b) living nonvirulent ... living virulent c) heat-killed virulent ... living nonvirulent d) living nonvirulent ... heat-killed virulent e) living virulent ... heat-killed nonvirulent

heat-killed virulent ... living nonvirulent

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? a) helicases, DNA polymerases, primase, ligase b) ligase, primase, DNA polymerases, helicases c) helicases, primase, DNA polymerases, ligase d) helicases, primase, ligase, DNA polymerases e) primase, helicases, DNA polymerases, ligase

helicases, primase, DNA polymerases, ligase

The two sugar-phosphate strands that form the rungs of a DNA double helix are joined to each other through _____ a) covalent bonds between carbon atoms in deoxyribose molecules b) ionic bonds between guanine and cytosine c) covalent bonds between nitrogen atoms in adenine and in thymine d) hydrogen bonds between nucleotide bases e) 5' deoxyribose and phosphate bonds

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.

Telomerase ________ a) splits telomeres b) speeds cell aging c) slows the rate of cancer cell growth d) is an enzyme that lengthens telomeres e) prevents the loss of centromeric DNA

is an enzyme that lengthens telomeres

Which of the following attributes of DNA is most crucial to its accurate duplication? a) its deoxyribose sugar and phosphate groups b) its specific base pairing and hydrogen bonding c) its helical nature and hydrogen bonding d) its phosphodiester linkages and complementary strands e) its specific sequence of bases

its specific base pairing and hydrogen bonding Explanation: It doesn't matter what the sequence of bases is. The structure of DNA guarantees that the sequence of bases that exists will be accurately copied.

The rate of elongation in prokaryotes is _____ the rate in eukaryotes. a) The rates are not comparable, because elongation only occurs in prokaryotes. b) much slower than c) much faster than d) about the same speed as e) sometimes faster and sometimes slower than

much faster than

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 set of enzymes is involved in nucleotide excision repair? a) nuclease, DNA polymerase, primase b) hydrolase, nuclease, and ligase c) DNA polymerase, helicase, primase d) ligase, nuclease, and primase e) nuclease, DNA polymerase, and ligase

nuclease, DNA polymerase, and ligase

The "beads on a string" seen in interphase chromatin are _____ a) histone tails b) looped domains c) nucleoids d) heterochromatin e) nucleosomes

nucleosomes

Monomers for the synthesis of DNA are called _____ a) monosaccharides b) fatty acids c) amino acids d) disaccharides e) nucleotides

nucleotides

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

The two strands of a DNA double helix are antiparallel. This means that _____. a) one strand is actually composed of RNA b) they both run in the 3' to 5' direction c) one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction d) only one of the two strands can be used as a template for replication, because DNA polymerase only works in one direction e) the two strands are mirror images

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

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? a) sterols because of the different variations on their ring structure b) 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 c) nucleoside triphosphates because of the ability to add and remove phosphate groups d) carbohydrates because they are found in abundance in all organisms e) amino acids because of all the ways they can join together

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

The experiments of Meselson and Stahl showed that DNA _____. a) is the genetic material b) replicates in a semiconservative fashion c) is composed of nucleotides d) contains complementary base pairing e) codes for the sequence of amino acids in proteins

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.

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 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 _____. a) DNA is made of nucleotides b) the genetic material of the phage is protein c) genes are on chromosomes d) bacteriophages can infect bacteria e) the genetic material of the phage is DNA

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.

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 _____ a) the protein and DNA of T4 b) a mixture of the DNA and proteins of both phages c) the protein of T4 and the DNA of T2 d) the protein and DNA of T2 e) the protein of T2 and the DNA of T4

the protein and DNA of T4

Chargaff found that for DNA _____. a) the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1 b) the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1 c) A + T = G + C d) the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1 e) A + T = 50% of the total bases

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

The information in DNA is contained in _____ a) the types of sugars used in making the DNA molecule b) the sequence of amino acids that makes up the DNA molecule c) the variation in the structure of nucleotides that make up the DNA molecule d) the sequence of nucleotides along the length of the two strands of the DNA molecule e) All of the listed responses are correct.

the sequence of nucleotides along the length of the two strands of the DNA molecule

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 _____ a) ligase b) topoisomerase c) relievase d) ribosomes e) primase

topoisomerase

Put the following DNA-containing entities in order according to the amount of DNA found in their genomes. a) virus, bacteria, eukaryote b) bacteria, virus, eukaryote c) bacteria, eukaryote, virus d) eukaryote, virus, bacteria e) They all have about the same amount of DNA.

virus, bacteria, eukaryote

Avery and his colleagues' 1944 experiment showed that DNA _____. a) uses three bases to code for one amino acid b) has two strands held together with hydrogen bonds c) contains adenine, guanine, thymine, and cytosine d) consists of sugars, phosphate groups, and bases e) was the substance that transformed the bacteria in Griffith's experiment

was the substance that transformed the bacteria in Griffith's experiment

What technique was most helpful to Watson and Crick in developing their model for the structure of DNA? a) transgenic animals b) radioactive labeling c) X-ray crystallography d) electrophoresis e) cloned DNA

x-ray crystallography