Deck 28: DNA Metabolism: Replication, recombination, and Repair

Question 1

Which of the following is a characteristic of Okazaki fragments?

A)about 20-30 nucleotides in length
B)newly synthesized large lagging strand fragments
C)synthesis performed in the 3'5' direction
D)initiated with an RNA primer

Answer 1

D

Question 2

Which of the following is a characteristic of the 3'-exonuclease activity of DNA polymerase I of E.coli?

A)It is relatively fast compared to polymerase activity.
B)It removes nucleotides that do not base pair at the 5'-end of the growing chain.
C)It is similar to the polymerase activity.
D)It is an editor of polymerase activity.

Answer 2

D

Question 3

Which of the following regarding DNA gyrase in E.Coli is correct?

A)It works to remove negative supercoiling introduced by the DnaB protein (helicase).
B)It is a topoisomerase that hydrolyzes ATP during its reaction mechanism.
C)Its mechanism involves the breaking of a single phosphoester bond in 1 strand of dsDNA.
D)It works to introduce positive supercoiling in DNA to overcome the torsion stress imposed upon unwinding.

Answer 3

B

Question 4

Which of the following is a shared characteristic of DNA polymerases?

A)They are strongly processive.
B)Incoming bases are paired with corresponding bases on the complementary strand within the polymerase active site.
C)Polymerization proceeds in a 3'5' direction.
D)Polymerization is antiparallel to template strand.

Question 5

Which of the following characteristics refers to the degree to which the enzyme remains associated with the template through successive cycles of nucleotide addition?

A)processivity
B)turn-over number
C)progression
D)semidiscontinuousness

Question 6

Which of the following enzymes removes the RNA primer from the Okazaki fragment?

A)DNA polymerase I
B)DNA ligase
C)DNA polymerase III
D)DNA gyrase

Question 7

Which of the following does a pair of b-subunits of DNA polymerase III form in order to tether the polymerase to the template,thus increasing the processivity of the polymerase?

A)a ligase
B)a sliding clamp
C)a primer binding site
D)a loop of DNA

Question 8

Which of the following enzymes seals nicks in dsDNA where a 3'-OH and 5'-phosphate are juxtapositioned?

A)DNA polymerase I
B)DNA gyrase
C)DNA polymerase III
D)DNA ligase

Question 9

Which of the following is a characteristic of replication of the E.coli circular chromosome?

A)Replication is unidirectional.
B)It initiates at a random position.
C)The unwinding of the duplex DNA is driven by the translocation of the DNA polymerase.
D)Torsional stress introduced in the duplex DNA is relieved by DNA gyrase.

Question 10

Which of the following types of mechanisms defines DNA replication?

A)dispersive
B)conservative
C)semiconservative
D)liberal

Question 11

Which of the following explains how the termination of DNA replication in E.coli occurs?

A)Tag protein binds the oriC locus on the DNA and acts as a helicase.
B)Ter protein binds the tag locus on the DNA and acts as a polymerase.
C)DnaC protein binds the DnaG locus on the DNA and acts as a gyrase.
D)Tus protein binds the Ter locus on the DNA and acts as contrahelicase.

Question 12

Eukaryotic cells have replication regions called replicators that occur every 3-300 kbp.Which of the following terms defines the units of replication?

A)replication forks
B)replication arms
C)replicons
D)replicators

Question 13

Which of the following enzymes catalyze the unwinding of the DNA double helix?

A)topoisomerases
B)helicases
C)ligases
D)gyrases

Question 14

Which of the following is a property of DNA polymerase III?

A)It is responsible for incorporating most of the nucleotides in the leading strand.
B)It is a large protein complex containing more than 5 subunits.
C)It synthesizes most of the leading strand prior to aiding in the synthesis of the lagging strand.
D)It has lesser processivity than DNA polymerase I.

Question 15

Which of the following is a feature of E.coli replication on the lagging strand?

A)It is primarily carried out by DNA polymerase I.
B)It is initially synthesized as Okazaki fragments.
C)It is synthesized continuously.
D)It is performed in a 3'5' direction of synthesis.

Question 16

How many distinct catalytic active sites does E.coli DNA polymerase I have on its single polypeptide chain?

A)1
B)2
C)3
D)4

Question 17

Which of the following defines SSBs?

A)supercoil stabilizing bodies
B)single-stranded bodies called Okazaki fragments
C)nucleases that hydrolyze single-stranded RNA primers
D)single-stranded DNA-binding proteins that prevent re-annealing

Question 18

Which of the following carries out removal of RNA primer,followed by replacement with DNA?

A)DNA polymerase I
B)DNA gyrase
C)DNA polymerase III
D)DNA ligase

Question 19

Which of the following occurs during DNA replication in E.coli?

A)Primase (DnaG)binds to a GC-rich region of dsDNA in oriC.
B)Helicase unwinds dsDNA downstream of the replication fork.
C)DNA ligase catalyzes the formation of phosphoester bonds on the leading strand.
D)DNA polymerase I hydrolyzes RNA from the 5' ends of Okazaki fragments.

Question 20

Which of the following is a characteristic of E.coli DNA polymerase I?

A)a 5'?3' exonuclease activity
B)a 3'?5' DNA polymerase activity
C)modest processivity (approximately 20 nucleotides)
D)does not require a primer for initiation

Question 21

Which of the following is NOT a part of homologous recombination?

A)ligation
B)nicking
C)EW or NS cleavage,resolution and re-ligation
D)strand division

Question 22

Which of the following proteins binds ssDNA,forming a nucleoprotein filament capable of strand invasion and homologous pairing in general recombination in E.coli?

A)RecA
B)RuvB
C)RuvA
D)RecBCD complex

Question 23

Progression through the cell cycle for eukaryotic cells is regulated through a series of checkpoints that depend on cyclins.Which of the following components do cyclins bind that can then regulate specific proteins by phosphorylation?

A)cyclin-dependent protein kinases (CDKs)
B)protein kinases
C)cyclin-dependent inhibitors
D)cAMPs

Question 24

Which of the following is a characteristic of transposons?

A)a major force in evolution
B)segments of DNA moved non-enzymatically in the genome
C)stable location within genome
D)range in size no more than hundreds of bps

Question 25

Which of the following is NOT a characteristic of RNA-directed DNA polymerase?

A)often uses a specific tRNA primer
B)found in retroviruses
C)synthesizes polynucleotides in the 3' to 5' direction
D)also called reverse transcriptase

Question 26

Which of the following is a function of the RecA protein in recombination events?

A)to produce an endonucleolytic nick on dsDNA
B)to aid in recognition of Chi site by the RecBCD complex
C)to initiate recombination
D)to catalyze the ATP-dependent DNA strand exchange reaction

Question 27

Which of the following is NOT a characteristic of retroviruses?

A)They use viral DNA as a template.
B)They must replicate through double-stranded DNA.
C)The retroviral RNA is reverse transcribed to dsDNA,which must be inserted into the host genome.
D)Their genome can lie dormant for years as a provirus in the host chromosome.

Question 28

Which of the following is NOT involved with RuvA,RuvB,and RuvC?

A)processing Holliday junctions into recombination products
B)aiding strand invasions of the 3'-ssDNA into homologous DNA duplexes
C)Holliday junction-specific helicase complex
D)dissociating the RecA filament and catalyzing branch migration

Question 29

AZT (3'-azido-2',3'-dideoxythymidine)is a drug that gets incorporated into growing viral DNA.What enzyme activity does it block?

A)reverse transcriptase
B)DNA ligase
C)DNA polymerase b (beta)
D)DNA polymerase a (alpha)

Question 30

Which of the following is an RNA-dependent DNA polymerase that carries the RNA template with it to synthesize repeats at the 3'-ends of chromosomes?

A)DNA ligase
B)telomerase
C)topoisomerase
D)DNA polymerase b (beta)

Question 31

Which of the following is NOT a part of the prereplication complex (pre-RC)in the initiation of replication in yeast?

A)MCM complex
B)CDKs
C)Cdc6p
D)ORC

Question 32

Which of the following is a characteristic of telomeres?

A)G-rich nucleotide sequences
B)structures at the end of eukaryotic chromosomes
C)eukaryotic counterpart to the prokaryotic g-complex
D)short (5-8 bp)tandemly repeated sequences

Question 33

Which of the following is NOT a characteristic of the DNA strand exchange reaction?

A)It is ATP-dependent.
B)It is catalyzed by RecA protein.
C)It requires DNA polymerase I.
D)Its complex has 3'-terminal ssDNA affinity for other DNA termini.

Question 34

BRCA1 protein functions in regulation of the cell cycle in response to DNA damage control,and BRCA2 protein participates in DNA repair by homologous recombination.Which of the following type(s)of cancers can occur as a result of mutations in BRCA1 and BRCA2 genes?

A)breast and ovarian
B)uterine
C)prostate
D)lung

Question 35

What explains why progeny may have new combinations of traits compared to their parents?

A)reverse transcriptase
B)cyclin-dependent protein kinase
C)genetic recombination
D)processivity

Question 36

Which of the following is NOT an activity the reverse transcriptases possess?

A)DNA ligase activity
B)RNA-directed DNA polymerase activity
C)RNase H activity
D)DNA-directed DNA polymerase activity

Question 37

Which protein moves along dsDNA using ATP-dependent helicase and nuclease activity during general recombination in E.coli?

A)RecBCD complex
B)RuvB
C)DNA polymerase I
D)DNA ligase

Question 38

Which of the following is the principal DNA polymerase in eukaryotic leading-strand DNA replication?

A)DNA polymerase a (alpha)
B)DNA polymerase b (beta)
C)DNA polymerase g (gamma)
D)DNA polymerase d (delta)

Question 39

Which of the following protein kinases acts on the prereplication complex (pre-RC)to trigger DNA replication in eukaryotic cells?

A)ORC
B)MCM
C)cyclin B-CDK
D)PKA

Question 40

Which of the following is NOT a common form of DNA damage?

A)replication errors resulting in a missing or incorrect base
B)transcription errors resulting in the substitution of bases
C)UV-induced base alterations,such as pyrimidine dimers
D)strand breaks at phosphodiester bonds or within deoxyribose rings

Question 41

Which of the following actions does the methyl-directed repair system take when it detects a mismatch in dsDNA?

A)It resynthesizes the newly replicated strand.
B)It corrects the DNA strand that is methylated.
C)It corrects the mismatch by changing the base on the not-yet-methylated strand.
D)It changes the base that is methylated.

Question 42

In base-excision repair,the first enzyme in the sequence is DNA glycosylase.Which of the following types of sites does the enzyme create?

A)ligase binding
B)apurinic or apyrimidinic
C)DNA polymerase I
D)DNA polymerase III binding

Question 43

Which of the following processes provides a mechanism for generating a variety of protein isoforms of immunoglobulins from a limited number of genes?

A)genetic recombination
B)DNA rearrangement
C)replication licensing
D)DNA ligation

Question 44

The repair of cyclobutane pyrimidine dimers involves bacterial photolyase.Which of the following cofactors does it use?

A)flavin and pterin
B)S-adenosylmethionine and ATP
C)CoA and CoQ
D)flavin and TPP

Question 45

Which of the following does NOT cause mutations in DNA?

A)errors in replication
B)physical insults on the cell,such as UV light
C)errors in transcription
D)chemical exposure

Question 46

Which of the following processes are B-cells,T-cells,and macrophages capable of that allows them to produce antibodies essential to the immune response?

A)replication rearrangement
B)complementarity modification
C)DNA replication
D)DNA rearrangement

Question 47

Which of the following nucleotides would replace T in a transversion mutation?

A)A
B)C
C)U
D)T

Question 48

Which of the following nucleotides would replace A in a transition mutation?

A)T
B)C
C)U
D)G

Question 49

Which of the following mutations can occur when the thymine analog,5-bromouracil,incorporates into DNA normally occupied by thymine?

A)T-A to A-T
B)G-C to C-G
C)U-A to A-U
D)C-G to T-A

Question 50

Nitrous acid causes the oxidative deamination of cytosine,producing uracil.Which of the following point mutations is the logical result?

A)T-A to G-C
B)C-G to T-A
C)C-G to G-C
D)T-A to A-T

Question 51

Which of the following terms defines the exchange of one base for another?

A)frameshift mutation
B)point mutation
C)transition mutation
D)transversion mutation

Question 52

Which of the following types of mutation causes misincorporation of all subsequent amino acids?

A)chemical
B)base shift
C)frameshift
D)transition

Question 53

Which of the following types of mutations most likely results from the alkylation of the oxygen on position 6 of guanine base,producing O⁶-methylguanine?

A)deletion
B)insertion
C)transition
D)frameshift

Question 54

Which of the following is NOT a step in mammalian nucleotide excision repair?

A)Lesions are recognized by XPA protein.
B)Sugar-phosphate backbone is cut in 1 place.
C)The resulting gap is filled in by DNA polymerases.
D)DNA backbone is closed with DNA ligase.

Question 55

Which of the following explains how the vast diversity of immunoglobulin sequences are created?

A)by DNA rearrangement
B)by large sections of DNA devoted to immunoglobulin formation
C)by susceptibility of the immunoglobulin genes to mutation
D)by sensitivity of formed immunoglobulin proteins to environmental factors

Question 56

Which of the following provides for genetic variability within species and,ultimately,the evolution of new species?

A)DNA repair and DNA glycosylase activity
B)DNA glycosylase activity and recombination
C)recombination and mutations
D)mutations and DNA glycosylase activity

Question 57

Which of the following regions of immunoglobulins forms the structural site complementary to some part of an antigen's structure?

A)immunoglobulin fold
B)hypervariable
C)hinge
D)constant heavy

Question 58

UV light promotes the formation of covalent bonds between nearby thymine residues in a DNA strand.Which of the following structures is created as a result of this?

A)a cyclobutyl ring called a thymidine trimer
B)a cyclohexyl ring called a thymidine trimer
C)a cyclobutyl ring called a thymidine dimer
D)a cyclohexyl ring called a thymidine dimer