DNA

What enzyme joins Okazaki fragments? (eText Concept 16.2) DNA ligase DNA polymerase primase helicase topoisomerase

a

What is the major difference between bacterial chromosomes and eukaryotic chromosomes? (eText Concept 16.3) Bacteria usually have a single circular chromosome whereas eukaryotes have several linear chromosomes. Eukaryotes have a single circular chromosome whereas bacteria have several linear chromosomes. The DNA molecules of bacterial chromosomes have a slightly different structure than those of eukaryotic chromosomes. There is no difference between bacterial and eukaryotic chromosomes. Bacterial chromosomes have much more protein associated with the DNA than eukaryotes.

a

Which of the following considerations was/were important in the choice of viruses and bacteria for early experiments on DNA? (eText Concept 16.3) They have short generation times. They can interact with each other. Their chromosomes have a simpler structure. They typically have relatively small genomes. All of the listed responses are correct.

a

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? (eText Concept 16.2) helicase, DNA polymerase, primase, ligase helicase, primase, DNA polymerase, ligase primase, helicase, DNA polymerase, ligase helicase, primase, ligase, DNA polymerase ligase, primase, DNA polymerase, helicase

b

In prokaryotes, the rate of elongation during DNA replication is __________ the rate in eukaryotes. (eText Concept 16.2) sometimes faster and sometimes slower than much faster than about the same as The rates are not comparable, because elongation only occurs in prokaryotes. much slower than

b

Telomerase __________. (eText Concept 16.2) prevents the loss of centromeric DNA is an enzyme that lengthens telomeres splits telomeres slows the rate of cancer cell growth speeds cell aging

b

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 __________. (eText Concept 16.2) primase DNA polymerase I DNA polymerase III ligase nuclease

b

The two strands of a DNA double helix are antiparallel. This means that __________. (eText Concept 16.2) 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 the two strands are mirror images

b

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?(eText 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. Because they are 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.

c

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? (eText Concept 16.2) 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. One of the strands is rapidly degraded, preventing the double helix from re-forming. The helicase modifies the DNA in such a way as to eliminate the affinity between the two strands.

c

The incorporation of an incorrect base into the DNA during replication __________. (eText Concept 16.2) 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 will almost certainly lead to the death of the cell is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur

c

Which of the following components is required for DNA replication? (eText Concept 16.2) ribosomes messenger RNA RNA primer sucrases proteases

c

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

c

DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments). (eText Concept 16.2) 3′ end ... 5′ end 5′ end ... 5′ end sugar group ... phosphate group 3′ end ... 3′ end 5′ end ... 3′ end

d

In his work with pneumonia-causing bacteria and mice, Griffith found that bacteriophages injected DNA into bacteria. 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. heat-killed pathogenic cells caused pneumonia.

d

In the "beads on a string" structure of unfolded chromatin, the "beads" are __________. (eText Concept 16.3) nucleoids genes looped domains nucleosomes heterochromatin

d

The experiments of Meselson and Stahl showed that DNA __________. (eText Concept 16.2) is composed of nucleotides contains complementary base pairing codes for the amino acid sequences of proteins replicates in a semiconservative fashion is the genetic material

d

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

d

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 __________. (eText Concept 16.2) relievase primase ligase topoisomerase helicase

d

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? Helicases and single-strand binding proteins work at the 59 end. DNA ligase works only in the 39 S59 direction. The origins of replication occur only at the 59 end. Polymerase can work on only one strand at a time. DNA polymerase can join new nucleotides only to the 39 end of a growing strand.

d

Which set of enzymes is involved in nucleotide excision repair? (eText Concept 16.2) hydrolase, nuclease, and ligase ligase, nuclease, and primase DNA polymerase, helicase, primase nuclease, DNA polymerase, and ligase nuclease, DNA polymerase, primase

d

n a nucleosome, the DNA is wrapped around satellite DNA. ribosomes. polymerase molecules. histones. a thymine dimer.

d

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules? A + T = G + T A = G G = T A + G = C + T A = C

e

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 polymerase primase nucleotides Okazaki fragments DNA ligase

e

As a result of proofreading by DNA polymerases, the overall error rate in the completed DNA molecule is approximately __________. (eText Concept 16.2) 1 error per 100 nucleotides 1 error per 1,000 nucleotides 1 error per 1,000,000 nucleotides 1 error per 1,000,000,000 nucleotides 1 error per 10,000,000,000 nucleotides

e

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′. (eText Concept 16.2) TGGAUA TGGATA UAUCCA ATAGGT TATCCA

e

Telomeres __________. (eText Concept 16.2) remain the same regardless of the frequency of DNA replication are shorter for younger individuals are found in both prokaryotic and eukaryotic cells get longer with each round of DNA replication get shorter with each round of DNA replication

e

Unlike prokaryotic DNA replication, replication of eukaryotic chromosomes __________. (eText Concept 16.2) involves two leading strands and no lagging strands has a single origin is error-free is semiconservative cannot be completed by DNA polymerase

e

Which of the following statements about replication origins is/are correct? (eText Concept 16.2) The DNA sequence at the origin of replication is recognized by specific proteins that bind to the origin. Bacterial chromosomes have a single origin of replication, but eukaryotic chromosomes have many origins. Replication proceeds in both directions from each origin. The two strands of DNA at the origin of replication are separated, creating a replication bubble. All of the listed responses are correct.

e

Which of the following statements is/are correct with regard to individuals with the disorder xeroderma pigmentosum? (eText Concept 16.2) These individuals usually have inherited defects in the nucleotide excision repair system. Cells in these individuals have difficulty repairing thymine dimers. These individuals are extremely sensitive to sunlight. These individuals have high rates of skin cancer. All of the listed responses are correct.

e

hich one of the following statements regarding DNA replication is correct? (eText Concept 16.2) Ligase assembles nucleotides into Okazaki fragments. Then polymerase joins these fragments together into a DNA strand. Ligase separates the two strands of the DNA double helix. Then, DNA polymerase synthesizes the leading strand and primase synthesizes the lagging strand. 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. The two strands of DNA separate, and nuclease enzymes digest one strand. Then, 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.

e