Quiz 30: DNA Replication and Repair

During replication of a DNA molecule, the daughter strands are not produced in exactly the same manner. One strand, the leading strand, is made toward the replication fork, while the lagging strand is made in fragments in the opposite direction. This difference in the synthesis of the two strands is the result of which of the following? A.) The two template strands are antiparallel, and DNA polymerase makes DNA only in the 5' to 3' direction B.) DNA polymerase is not efficient enough to make two "good" strands of DNA C.) The cell does not contain enough nucleotides to make two complete strands D.)The lagging strand is the result of DNA breakage due to UV light

A.) The two template strands are antiparallel, and DNA polymerase makes DNA only in the 5' to 3' direction

Which of the following is not associated with the function of DNA polymerase? A.) it is associated with a sliding clamp only on the leading strand B.) it requires a primer to work C.) it catalyzes the addition of nucleotides only in the 5'→ 3' direction D.) its exonuclease activity is involved in proofreading

A.) it is associated with a sliding clamp only on the leading strand

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? A.) the origins of replication occur only at the 5' end B.) DNA polymerase can join new nucleotides only to the 3' end of a pre-existing strand C.)helicases and single-strand binding proteins work at the 5' end D.) DNA ligase works only in the 3' → 5' direction

B.) DNA polymerase can join new nucleotides only to the 3' end of a pre-existing strand

The statement "DNA replicates by a semiconservative mechanism" means that: A.) first one DNA strand is copied, and then the other strand is copied B.) each double helix consists of one old and one newly synthesized strand C.) the two strands of a double helix have identical base sequences D.) some portions of a single DNA strand are old, and other portions are newly synthesized E.) only one strand of DNA is copied

B.) each double helix consists of one old and one newly synthesized strand

Hypoxanthine is an uncommon base that can sometime be found in DNA opposite thymine. It arises from the spontaneous loss of amino groups from adenine and does not properly base pair with thymine the way adenine does. What combination of proteins could repair such damage? A.) telomerase, primase, DNA polymerase B.) nuclease, DNA polymerase, DNA ligase C.) telomerase, helicase, single-strand binding protein D.) DNA ligase, replication fork proteins, adenylyl cyclase

B.) nuclease, DNA polymerase, DNA ligase

If you could engineer an activity into DNA polymerase to allow both strands to follow the replication fork, what would this additional activity be? A.) the ability to synthesize DNA without using a template B.) the ability to synthesize in the 3'→5' direction C.) the ability to proofread in the 5'→3' direction D.) the ability to begin DNA synthesis without a primer

B.) the ability to synthesize in the 3'→5' direction

What do topoisomerases do? A.) synthesize DNA B.) synthesize RNA primers C.) break and rejoin DNA to reduce torsional stress D.) prevent single DNA strands from joining to form a double helix E.) join Okazaki fragments

C.) break and rejoin DNA to reduce torsional stress

What does synthesis of a new DNA strand usually begin with? A.) a thymine dimer B.) an Okazaki fragment C.) a DNA primer D.) an RNA primer E.) DNA ligase

D.) an RNA primer

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 in a CsCl gradient. What density distribution of DNA would you expect in this experiment? A.) one intermediate-density band B.) one high-density band and one low-density band C.) one high-density band and one intermediate-density band D.) one low-density band and one intermediate-density band

D.) one low-density band 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? A.) DNA polymerase B.) nucleotides C.) primase D.) Okazaki fragments E.) DNA ligase

E.) DNA ligase