genetics ch 10

35) During replication, the double helix undergoes torsional stress during strand separation and polymerase activity. Several proteins are employed to counter this stress and assist strand separation. Which of the following proteins involved with this process is defined incorrectly below? a) SSB: promote the separation of complementary sequence. b) Helicase: unwinding of the parental DNA strands. c) Topoisomerase I: removes and introduces supercoils one at a time. d) Topoisomerase II: removes and introduces supercoils two at a time. e) Gyrase: topoisomerase II in E. coli.

c

36) Which of the following prokaryotic replication events is incorrect? a) Interaction of prepriming proteins with oriC, such as DnaA, DnaB, and DnaC. b) Initiation of Okazaki fragments on the lagging strand carried out by the primosome, a protein complex of primase and DNA helicase. c) RNA primers are covalently extended with deoxynucleotides by Pol I d) The replisome contains two Pol III holoenzymes, one for the leading and one for lagging strands. e) Only one of the two Pol III holoenzymes contains a primosome.

c

41) The RNA containing enzyme that participates in the addition of the telomeric ends of the chromosome is known as: a) Replicase b) Gyrase c) Telomerase d) Ligase e) Polymerase V

c

45) Telomerase inhibitors are thought to be one possible treatment for which of the following? a) Aging b) Progeria c) Cancer d) Aging and Progeria e) Progeria and Cancer

c

6) The work of Meselson and Stahl: a) Showed that DNA replication semiconservative, which means that the parental double helix is conserved. b) Used the radioisotope 3H-thymidine in conjunction with centrifugation to separate DNA on the basis of size c) Showed that the DNA, after one round of replication, was of intermediate density thereby showing that the DNA molecules contained one parent strand and one new strand. d) All of these e) None of these

c

8) The proof that eukaryotic chromosomal replication was a semi-conservative process: a) Used 3H-thymidine to label E. coli DNA. b) Used 3H-thymidine to label human cell DNA. c) Relied on the assumption that each chromosome in the broad bean consisted of a single DNA molecule. d) Did not require the fact that each chromosome consists of a single strand of DNA. e) None of these

c

Which of the following choices shows the template strand of DNA used for replication? a) 3'---ATCGGGAAATTCGGA—5' b) 5'---ATCGGGAAATTCGGA---3' c) 3'---TAGCCCTTTAAGCCT---5' d) 3'---TAGCCCTTTAAGCCT---5' e) 5'---UAGCCCUUUAAGCCU---3'

c

19) Which of the following does not replicate in a bidirectional format? a) Lambda phage b) E. coli c) SV40 d) Coliphage P2 e) All of these replicate bidirectionally

d

2) Which of the following statements is not true regarding DNA replication? a) DNA replication occurs in a semi-conservative manner. b) DNA replication begins at unique initiation points c) DNA replication proceeds bidirectionally from the initiation point. d) DNA replication proceeds in one direction from the initiation point. e) All of these are false

d

27) A researcher is attempting to replicate DNA in vitro. All necessary components are added, however, the DNA that is used does not have a free 3' hydroxyl. What kind of result is expected? a) The DNA will replicate at a normal rate b) The DNA will replicate but at a much slower rate c) The DNA will not replicate because DNA polymerase will not be active d) The DNA will not replicate because DNA polymerase can not add dNTPs to the existing DNA e) The DNA will not replicate because the free 3'hydroxyl is what catalyzes the DNA synthesis Answer: d

d

33) Complementary strands of a DNA double helix have opposite chemical polarity but are synthesized in the same direction (replication fork movement). This is accounted for by: a) Using a 3'→5' polymerase to synthesize the lagging strand. b) Using discontinuous synthesis on the leading strand. c) Using the polymerase activity of DNA ligase. d) Using the 5'→3' polymerase activity of Pol III to synthesize multiple short segments which are later covalently joined. e) None of these

d

4) In order for DNA to replicate in a semi-conservative manner, what must occur? 1. The double stranded parent DNA molecule must be separated by breaking the hydrogen bonds between the nitrogenous bases 2. Both parent strands of DNA must serve as a template for the synthesis of the new strands 3. The parent strands of DNA must re-anneal after serving as a template for the synthesis of new DNA. a) 1 b) 2 c) 3 d) 1 and 2 e) 2 and 3

d

11) When John Cairns first visualized the replication of E. coli chromosomes in 1963 what did he conclude? 1. The chromosomes of E. coli are circular structures that exist as υ-shaped intermediates during replication. 2. The unwinding of the two complementary parental strands and their semiconservative replication occur simultaneously or are closely coupled. 3. Semiconservative replication of the E. coli chromosome started at a specific site, and proceeded sequentially and unidirectionally around the circular structure a) 1 b) 2 c) 3 d) 1 and 2 e) All of these

e

22) Eukaryotic chromosomal replication: 1. Is bidirectional 2. Occurs from multiple origins 3. Has sequence-specific origins (termed autonomously replicating sequences) a) 1 b) 2 c) 3 d) 2 and 3 e) All of these

e

24) Which of the following must be present in order for DNA polymerase to be active? 1. Mg2+ 2. dNTPs 3. Existing DNA template with a free 3' end a) 1 b) 2 c) 3 d) 1 and 3 e) All of these

e

28) Which of the following is a true function of DNA Polymerase I? 1. Replicase 2. 5'→3' exonuclease 3. 3'→5' exonuclease a) 1 b) 2 c) 3 d) 1 and 2 e) 2 and 3

e

37) Rolling circle replication: a) Is only found in viruses and bacteria. b) Proceeds bidirectionally. c) Is initiated by an exonucleolytic cleavage event. d) Can only produce single-stranded progeny molecules. e) Generates single-stranded tails longer than length of the parent circular molecule.

e

42) Which of the following statements about telomerase are true: 1. It extends the 3' end of a linear chromosome one repeat at a time. 2. It uses a built-in DNA to act as a template for synthesis of the telomeric repeat. 3. Without telomerase, linear chromosomes would become progressively shorter. a) 1 b) 2 c) 3 d) 1 and 2 e) 1 and 3

e

43) Which subunit of the Pol III enzyme forms a ring-like structure around DNA, acting like PCNA in eukaryotes, in order to increase the enzyme's processivity? a) θ b) α c) ε d) τ e) β

e

15) A replication bubble is: a) A localized region of DNA strand separation b) A localized region of RNA strand separation c) A localized region of DNA strand attachment d) All of these e) None of these

a

18) Schnös and Inman demonstrated that bidirectional replication occurs by: a) visualizing phage replication forks in conjunction with denaturation mapping by electron microscopy b) visualizing phage replication forks using gel electrophoresis c) observing the υ-shaped replicative structure of the lambda chromosome d) All of these e) None of these

a

31) Proofreading activities of E. coli DNA polymerases is carried out by: a) Polymerase I by the 3'→5' exonuclease activity b) Polymerase I by the 5'→3' exonuclease activity c) Polymerase III by the 3'→5' exonuclease activity d) Polymerase III by the 5'→3' exonuclease activity e) Polymerase IV by the 5'→3' endonuclease activity

a

34) DNA replication requires a free 3'-OH to initiate polymerase activity. This is accomplished by synthesizing: a) A temporary RNA primer removed by Pol I. b) A temporary RNA primer removed by Pol III. c) A permanent DNA primer synthesized by Pol III. d) A permanent DNA primer synthesized by Pol I. e) DNA replication does not require a free 3'-OH

a

38) One similarity between prokaryotic and eukaryotic DNA replication is: a) Distinct leading and lagging strands b) RNA primer length c) Multiple origins of replication d) Having DNA replication occur during a specific portion of the cell cycle. e) Use of two different polymerases for leading and lagging strand synthesis.

a

40) In eukaryotes, two DNA polymerases were found to be essential to leading and lagging strand synthesis of the SV40 virus. They are: a) α,δ b) β,α c) θ,α d) Χ,β e) ξ,α

a

9) Which of the following technologies aided in the visualization of the replication forks in E. coli? a) Autoradiography b) Gel electrophoresis c) SDS-PAGE d) Southern blotting e) HPLC

a

1) DNA replication occurs in which manner? a) Conservative b) Semi-Conservative c) Dispersive d) Conservative and Semi-Conservative e) Semi-Conservative and Dispersive

b

10) E. coli chromosomes: a) Replicate in a unidirectional pattern from a single, unique origin, called oriC. b) Adopt a υ-shaped conformation during replication. c) Consist of two Y-shaped replication forks which move in same direction d) Have AT-rich regions at the origin of replication to maintain a tight conformation between strands, this facilitates the formation of the replication bubble. e) None of these

b

16) In the yeast Saccharomyces cerevisiae, segments of chromosomal DNA that allow a fragment of circularized DNA to replicate as an independent unit are known as: a) Bidirectionally Replicating Units b) Autonomously Replicating Sequences c) Extrachromosomally Replicating Elements d) Unique Origins of Replication e) None of these

b

17) What purpose is served by DNA Ligase? a) To break hydrogen bonds in the DNA structure b) To seal single stranded breaks in the DNA double helices c) To seal double stranded breaks in the DNA single helices d) All of these e) None of these

b

26) The direction of DNA synthesis is: a) Always 3'→5' b) Always 5'→3' c) Both 5'→3' and 3'→5' d) Neither 5'→3' or 3'→5' e) DNA synthesis is not ordered. It is a random process

b

30) Which of the following characteristics is not a commonality between prokaryotic and eukaryotic DNA polymerases? a) 3'→5' exonuclease activity. b) They consist of a single polypeptide chain. c) 5'→3' polymerase activity. d) They require a free 3'-OH end on a pre-existing primer. e) Prokaryotic and eukaryotic DNA polymerases share all of these characteristics.

b

32) The 3'→5' exonuclease activities of DNA polymerases read nascent strands as they are synthesized, removing any mispaired nucleotides at the 3′ termini of primer strands. This action is known as: a) Rereading b) Proofreading c) Editing d) Splicing e) Lysing

b

39) Eukaryotes were found to have multiple replicons per chromosome by: a) 2H thymidine pulse experiments b) 3H thymidine pulse-chase experiments c) 1H thymidine pulse experiments d) 2H thymidine pulse-chase experiments e) None of these

b

44) Telomere length has not been correlated with: a) Aging b) Sex determination c) Progeria d) Cancer e) All of these

b

5) Meselson and Stahl are best known for demonstrating that: a) DNA replication occurs in a conservative manner in E. coli b) DNA replication occurs in a semi-conservative manner in E. coli c) DNA replication occurs in a conservative manner in eukaryotes d) DNA replication occurs in a semi-conservative manner in eukaryotes e) None of these

b

7) The idea that eukaryotic chromosomes replicate semiconservatively was supported by Taylor et al, in experiments using 3H-thymidine labeled DNA from ______: a) E. coli , and saw that the DNA was of intermediate density after one round of replication b) Vicia faba, and saw that only one of the chromatids of each pair was radioactive after a second round of c-metaphase. c) Vicia faba , and saw that only one of the chromatids of each pair was radioactive after a single round of c-metaphase. d) E. coli , and saw that the DNA was of light density after one round of replication e) None of these

b

12) Since the parental double helix must rotate 360° to unwind each gyre of the helix, during the semi-conservative replication of the bacterial chromosome, some kind of "swivel" must exist. What do geneticists now know that the required swivel is? a) Topoisomerase b) Helicase c) A transient single-strand break produced by the action of topoisomerases d) A transient single-strand break produced by the action of helicases e) A transient single-strand break produced by the action of Ligase

c

20) Consider the DNA template to be used for replication: 3'—ATCGGGAAATTCGGA—5' Which of the following choices shows the correctly replicated new strand of DNA? a) 3'---ATCGGGAAATTCGGA—5' b) 5'---ATCGGGAAATTCGGA---3' c) 3'---TAGCCCTTTAAGCCT---5' d) 3'---TAGCCCTTTAAGCCT---5' e) 5'---UAGCCCUUUAAGCCU---3'

c

23) Which of the following enzymes catalyzes DNA synthesis? a) DNA Ligase b) DNA Helicase c) DNA Polymerase d) DNA Gyrase e) None of these

c

25) A researcher is attempting to replicate DNA in vitro. He adds all of the components to the tube except Mg2+. What kind of result can he expect to observe? a) The DNA will replicate at a normal rate b) The DNA will replicate but at a much slower rate c) The DNA will not replicate because DNA polymerase will not be active d) The DNA will not replicate because DNA polymerase was not added e) The DNA will not replicate because the Mg2+ is what catalyzes the DNA synthesis

c

29) Which DNA polymerase molecule acts as the replicase in E. coli? a) DNA Polymerase I b) DNA Polymerase II c) DNA Polymerase III d) DNA Polymerase IV e) DNA Polymerase V

c

3) The synthesis of new DNA from parental DNA involves which three steps? a) Replication, transcription, and translation b) Replication, gene expression and translation c) Initiation, elongation, and termination d) Initiation, gene expression, and transcription e) Elongation, termination, and gene expression

c

13) How many origins of replication are typically found in a bacterial or viral chromosome? a) One b) Two c) Three d) Four e) Five

a

14) In the E. coli chromosome the origin of replication, called oriC, is characterized as being rich in: a) A-T base pairs b) A-G base pairs c) C-G base pairs d) C-T base pairs e) G-T base pairs

a