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Problem 1
Which of the following is not a property of DNA polymerase? a. It adds dNTPs only in the 5'→3' direction. b. It requires a primer to begin synthesis. c. It opens the two strands of DNA at the replication fork. d. Its exonuclease activity is involved in proofreading.
Problem 2
What is the function of primase? a. synthesis of the repetitive, short double-stranded DNA sequences required by DNA polymerase b. synthesis of a short RNA strand that is complementary to single-stranded DNA c. closing the gap at the 3′ end of DNA after excision repair d. removing primers and synthesizing a short section of DNA to replace them
Problem 3
How are Okazaki fragments synthesized? a. by using the leading-strand template, and synthesizing 5'→3' b. by using the leading-strand template, and synthesizing 3'→5' c. by using the lagging-strand template, and synthesizing 5'→3' d. by using the lagging-strand template, and synthesizing 3'→5'.
Problem 4
Telomerase synthesizes DNA in the direction.
Problem 5
Researchers design experiments so that only one thing is different between the treatments that are being compared. In the Hershey–Chase experiment, what was this single difference?
Problem 6
Analyze the following statements about DNA synthesis. Select True or False for each statement. T/F An RNA polymerase is essential for DNA synthesis. T/F Okazaki fragments would be unnecessary if DNA polymerase could synthesize DNA in both the 3'→5' and 5'→3' directions. T/F DNA ligase is used more frequently on the lagging strand than on the leading strand. T/F Toposiomerase is required to separate the two strands of DNA at the replication fork.
Problem 7
How does telomerase prevent linear chromosomes from shortening during replication?
Problem 8a
What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage? (a) the polarity of each DNA strand
Problem 8b
What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage? (b) the antiparallel orientation of strands in the double helix
Problem 8c
What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage? (c) the energy differences between correct and incorrect base pairs
Problem 8d
What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage? (d) the regularity of DNA's structure
Problem 9
In the late 1950s, Herbert Taylor grew bean root-tip cells in a solution of radioactive thymidine (a precursor to one of the deoxyribonucleotides in DNA) and allowed them to undergo one round of DNA replication. He then transferred the cells to a solution without radioactive thymidine, allowed them to replicate again, and examined their chromosomes for the presence of radioactivity. His results are shown in the following figure, where red indicates a radioactive chromatid. (b) What would the results of Taylor's experiment be if eukaryotes used a conservative mode of DNA replication?
Problem 9a
In the late 1950s, Herbert Taylor grew bean root-tip cells in a solution of radioactive thymidine (a precursor to one of the deoxyribonucleotides in DNA) and allowed them to undergo one round of DNA replication. He then transferred the cells to a solution without radioactive thymidine, allowed them to replicate again, and examined their chromosomes for the presence of radioactivity. His results are shown in the following figure, where red indicates a radioactive chromatid. (a) Draw labeled diagrams of double-stranded DNA molecules that explain the pattern of radioactivity observed in the sister chromatids after the first and second rounds of replication.
Problem 10
The graph that follows shows the survival of four different E. coli strains after exposure to increasing doses of ultraviolet light. The wild-type strain is normal, but the other strains have a mutation in either a gene called uvrA, a gene called recA, or both. (a) Which strains are most sensitive to UV light? Which strains are least sensitive?
Problem 10b
The graph that follows shows the survival of four different E. coli strains after exposure to increasing doses of ultraviolet light. The wild-type strain is normal, but the other strains have a mutation in either a gene called uvrA, a gene called recA, or both. (b) What are the relative contributions of these genes to the repair of UV damage?
