DNA Structure and Replication

B okazaki fragments prevent elongation in the 3 to 5

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B Okazaki fragments prevent elongation in the 3' to 5' direction. C the polarity of the DNA molecule prevents addition of nucleotides at the 3' end. D replication must progress toward the replication fork. E DNA polymerase can only add nucleotides to the free 3' end. ____ 42. Replicating the lagging strand of DNA-that is, adding bases in the 3' 5' direction-utilizes which of the following? A DNA ligase B RNA primers C Okazaki fragments D A and B only E A, B, and C ____ 43. What kind of molecule or substance is the primer that is used to initiate the synthesis of a new DNA strand? A RNA B DNA C protein D phosphate E sulfur ____ 44. What is the function of topoisomerase? A relieving strain in the DNA ahead of the replication fork B elongation of new DNA at a replication fork by addition of nucleotides to the existing chain C the addition of methyl groups to bases of DNA D unwinding of the double helix E stabilizing single-stranded DNA at the replication fork ____ 45. What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A synthesize RNA nucleotides to make a primer B catalyze the lengthening of telomeres C join Okazaki fragments together D unwind the parental double helix E stabilize the unwound parental DNA ____ 46. All of the following are functions of DNA polymerase in DNA replication except A covalently adding nucleotides to the new strands. B proofreading each added nucleotide for correct base pairing. C replacing RNA primers with DNA. D initiating a polynucleotide strand. E none of the above ____ 47. Which of the following help to hold the DNA strands apart while they are being replicated? A primase B ligase C DNA polymerase D single-strand binding proteins E exonuclease ____ 48. Which of these mechanisms ensures that the DNA sequence in the genome remains accurate? A proofreading during DNA replication B mismatch repair C excision repair D complementary base pairing during DNA replication E all of the above ____ 49. Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight because their cells have an impaired ability to A replicate DNA. B undergo mitosis. C exchange DNA with other cells. D repair thymine dimers. E recombine homologous chromosomes during meiosis. ____ 50. Which of the following is analogous to telomeres? A the pull tab on a soft drink can B the two ends of a shoelace C the central spindle that a CD fits around while in the case D the mechanism of a zipper that allows the separated parts to be joined E the correct letters used to replace errors in a document after they have been deleted in a word processor ____ 51. A eukaryotic cell lacking telomerase would A have a high probability of becoming cancerous. B produce Okazaki fragments. C be unable to repair thymine dimers.
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