Chapter 16 Pre-Test

A new DNA strand elongates only in the 5' to 3' direction because A) DNA polymerase begins adding nucleotides at the 5' end of the template. 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.

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

Which of the following best describes the addition of nucleotides to a growing DNA chain? A) A nucleoside triphosphate is added to the 5' end of the DNA, releasing a molecule of pyrophosphate. B) A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate. C) A nucleoside diphosphate is added to the 5' end of the DNA, releasing a molecule of phosphate. D) A nucleoside diphosphate is added to the 3' end of the DNA, releasing a molecule of phosphate. E) A nucleoside monophosphate is added to the 3' end of the DNA.

The leading and the lagging strands differ in that A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. B) the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. C) the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together. D) both A and B E) both A and C

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

What is the function of DNA polymerase? A) to unwind the DNA helix during replication B) to seal together the broken ends of DNA strands C) to add nucleotides to the end of a growing DNA strand D) to degrade damaged DNA molecules E) to rejoin the two DNA strands (one new and one old) after replication

What determines the nucleotide sequence of the newly synthesized strand during DNA replication? A) the particular DNA polymerase catalyzing the reaction B) the relative amounts of the four nucleoside triphosphates in the cell C) the nucleotide sequence of the template strand D) the primase used in the reaction E) both A and D

Which enzyme catalyzes the elongation of a DNA strand in the 5' 3' direction? A) primase B) DNA ligase C) DNA polymerase D) topoisomerase E) helicase

The strands that make up DNA are antiparallel. This means that A) the twisting nature of DNA creates nonparallel strands. B) the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. C) base pairings create unequal spacing between the two DNA strands. D) one strand is positively charged and the other is negatively charged. E) one strand contains only purines and the other contains only pyrimidines.

Which of the following statements is false when comparing prokaryotes with eukaryotes? A) The prokaryotic chromosome is circular, whereas eukaryotic chromosomes are linear. B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many. C) The rate of elongation during DNA replication is higher in prokaryotes than in eukaryotes. D) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not. E) Eukaryotes have telomeres, and prokaryotes do not.

In an analysis of the nucleotide composition of DNA, which of the following is true? A) A = C B) A = G and C = T C) A + C = G + T D) G + A = T + C E) both C and D

What kind of chemical bond is found between paired bases of the DNA double helix? A) hydrogen B) ionic C) covalent D) sulfhydryl E) phosphate

The DNA double helix has a uniform diameter because ________, which have two rings, always pair with ________, which have one ring. A) purines; pyrimidines B) pyrimidines; purines C) deoxyribose sugars; ribose sugars D) ribose sugars; deoxyribose sugars E) nucleotides; nucleoside triphosphates

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately, what percentage of the nucleotides in this sample will be thymine? A) 12 B) 24 C) 31 D) 38 E) It cannot be determined from the information provided.

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

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

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

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

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

Which of the following statements about telomeres is correct? A) They contain multiple copies of a short RNA sequence. B) They are present at the ends of eukaryotic chromosomes. C) They can be extended by an enzyme called telomerase. D) both A and B E) both B and C

A eukaryotic cell lacking active telomerase would A) be unable to take up DNA from the surrounding solution. B) be unable to identify and correct mismatched nucleotides. C) experience a gradual reduction of chromosome length with each replication cycle. D) have a greater potential to become cancerous. E) be unable to connect Okazaki fragments.

The elongation of the leading strand during DNA synthesis A) progresses away from the replication fork. B) occurs in the 3' → 5' direction. C) produces Okazaki fragments. D) depends on the action of DNA polymerase. E) does not require a template strand.

The spontaneous loss of amino groups from adenine results in hypoxanthine, an unnatural base, opposite thymine in DNA. What combination of molecules could repair such damage? A) nuclease, DNA polymerase, DNA ligase B) telomerase, primase, DNA polymerase C) telomerase, helicase, single-strand binding protein D) DNA ligase, replication fork proteins, adenylyl cyclase E) nuclease, telomerase, primase

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

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

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? A) one high-density and one low-density band B) one intermediate-density band C) one high-density and one intermediate-density band D) one low-density and one intermediate-density band E) one low-density band

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

The most reasonable inference from the observation that defects in DNA repair enzymes contribute to some cancers is that A) cancer is generally inherited. B) uncorrected changes in DNA can lead to cancer. C) cancer cannot occur when repair enzymes work properly. D) mutations generally lead to cancer. E) cancer is caused by environmental factors that damage DNA repair enzymes.