Deck 26: DNA Restructuring: Repair, Recombination, Rearrangement, Amplification

Question 1

What is the correct order of enzyme activities required for nucleotide excision repair?

A)exonuclease, helicase, polymerase, ligase
B)exinuclease, helicase, polymerase, ligase
C)exonuclease, polymerase, ligase, helicase
D)exinuclease, polymerase, ligase, helicase
E)exonuclease, ligase, polymerase, helicase

Answer 1

B

Question 2

One mechanism to introduce greater diversity into antibody sequences is somatic hypermutation. What enzyme is responsible for somatic hypermutation in the DNA sequences that code for antibodies?

A)deoxyadenosine deaminase
B)deoxycytidine deaminase
C)deoxyadenosine transaminase
D)purine-pyrimidine transposase
E)none of the above

Answer 2

B

Question 3

How does RecA bring about strand exchange?

A)RecA acts as a helicase, unwinding DNA in localized regions
B)RecA monomers bind to ssDNA to form a nucleoprotein filament
C)RecA monomers interact only with ssDNA and immediately dissociate when binding to dsDNA
D)RecA forms a tetramer that wraps around DNA at specific sites that must be cleaved by a nuclease
E)none of the above

Answer 3

B

Question 4

In mismatch repair coupled to replication, which of the following relates a correct sequence of events?

A)daughter strand identification, mismatch identification, cleavage of daughter strand, helicase, polymerase, ligase
B)daughter strand identification, mismatch identification, helicase, cleavage of daughter strand, polymerase, ligase
C)mismatch identification, daughter strand identification, cleavage of daughter strand, helicase, polymerase, ligase
D)mismatch identification, daughter strand identification, helicase, cleavage of daughter strand, polymerase, ligase
E)mismatch identification, helicase, daughter strand identification, cleavage of daughter strand, polymerase, ligase

Question 5

Which of the following transposable elements is correctly defined?

A)insertion sequence: protein-encoding gene flanked by two insertion sequences
B)composite transposon: protein-encoding gene + transposase and resolvase genes flanked by two insertion sequences
C)class II transposon: protein-encoding gene + resolvase gene flanked by two insertion sequences
D)class III transposon: results from infection of a bacteriophage such as Mu
E)none of the above

Question 6

Which of the following types of DNA repair is often coupled with transcription?

A)photoreactivation
B)base excision repair
C)replication
D)nucleotide excision repair
E)all of the above

Question 7

Methylation of guanine to produce O⁶-methylguanine (mG)results in what change to DNA?

A)mG frequently pairs with thymine resulting in a GC $\rarr$ AT mutation
B)mG loses its methoxy group resulting in hydrogen bonding with adenine and a bulge in the double helix
C)mG is prone to deamination and eventually, depurination
D)repair of mG adducts uses a radical mechanism that has the potential to further damage adjacent bases, particularly thymine
E)none of the above

Question 8

Which of the following coenzymes forms the photochemical reaction center of DNA photolyase?

A)NADH
B)thiamine pyrophosphate
C)biotin
D)FADH^-
E)5-methyltetrahydrofolate

Question 9

What role does integration host factor (IHF)play in site-specific recombination during phage $\lambda$ lysogeny?

A)binds host DNA forcing a 90 ^$\circ$ bend
B)supercoils phage DNA
C)cleaves host and phage DNA at specific sites to create sticky ends
D)ligates host and phage DNA once recombination occurs
E)all of the above

Question 10

The repair of a double-strand break can be accomplished by ______________, which requires the Ku70/80 protein to _______________________.

A)nonhomologous end joining; catalyze blunt end ligation
B)nonhomologous end joining; bind to both ends of the break
C)homologous recombination; catalyze blunt end ligation
D)homologous recombination; bind to both ends of the break
E)none of the above

Question 11

Which of the following the represents the correct sequence of events for the Holiday model of homologous recombination?

A)nicking, strand invasion, branch migration, ligation, crossed strand breakage, rejoining
B)nicking, strand invasion, branch migration, crossed strand breakage, ligation, rejoining
C)nicking, strand invasion, ligation, branch migration, crossed strand breakage, rejoining
D)nicking, strand invasion, ligation, branch migration, isomerization, crossed strand breakage, rejoining
E)nicking, strand invasion, branch migration, isomerization, crossed strand breakage, ligation, rejoining

Question 12

What is the causative agent in the formation of a cyclobutane thymine dimer?

A)benzo[a]pyrene
B)N-methyl-N'nitro-N-nitrosoguanidine
C)methylnitrosourea
D)ethylmethanesulfonate
E)ultraviolet radiation

Question 13

Using the figure below, what is the first bond broken in the base excision repair process?

A)1
B)2
C)3
D)4
E)5

Question 14

In antibody light chain production, combination of V and J regions occurs at the _____ level; combination of J and C regions occurs at the _____ level.

A)DNA; DNA
B)DNA; RNA
C)DNA; protein
D)RNA; RNA
E)RNA; protein

Question 15

Which is a possible outcome when guanine is oxidized to 8-oxoguanine in the following segment of DNA?

A) is the only possible outcome
B) is the only possible outcome
C) is the only possible outcome
D)both and are possible outcomes
E)both and are possible outcomes

Question 16

In order for lysogeny to occur, the enzyme ______________ must insert the phage DNA into a specific site in the bacterial chromosome.

A)ligase
B)lysogenase
C)helicase
D)integrase
E)none of the above

Question 17

Which of the following is formed by oxidation of a DNA base?

A)uracil
B)8-oxoguanine
C)7-methylguanine
D)thymine dimer
E)all of the above

Question 18

The introduction of DNA into a bacterial cell by first packaging the DNA into a phage particle is referred to as _____________.

A)transduction
B)transformation
C)transposition
D)conjugation
E)illegitimate recombination

Question 19

Which base or bases is/are methylated to identify the original template strand of replicated DNA?

A)A
B)C
C)G
D)A and G
E)C and G

Question 20

What is a common trigger for the bacterial SOS response?

A)thymine starvation
B)DNA cross-linking agents such as mitomycin C
C)ultraviolet radiation
D)mutation of DNA replication genes
E)all of the above

Question 21

What is contained within a homogeneously staining region?

A)a series of several replication origins
B)a sequence of genes all under control of one promoter
C)tandem duplicates of a specific gene
D)a region of DNA created by a retrovirus
E)none of the above

Question 22

Using the following DNA segment, show how microsatellite instability is present through a 2-base deletion as a result of loop creation within the A-C repeating sequence. Give the sequence after the first round of replication (with loop)and after the second round of replication.
Template strand: 3'-C-A-C-A-C-A-C-A-C-A-5'

Question 23

Show the common base pair seen between 8-oxoguanine and adenine.

Question 24

A transposable element in a eukaryotic cell is called a _____________.

A)retrotransposon
B)long terminal repeat
C)oncogene
D)replicative transposon
E)composite transposon

Question 25

Given the following DNA segments, show the intermediate structure that would be produced following isomerization during homologous recombination.