Molecular Biology Exam questions
and answers graded A+
RecA protein is required for: - ANS✅✅Recombination (repair) and SOS repair
When is homology-directed repair (HDR) most likely to be mutagenic (least likely to exactly replace
missing sequence)? - ANS✅✅During G1, because repair template is usually a homologous
chromosome
__________ make up the heterodimer that recognizes broken DNA ends. - ANS✅✅Ku70 and Ku80
The D-loop is the structure formed when a single-stranded overhang invades the duplex of the repair
template (strand invasion). Which of the following is TRUE regarding strand invasion: - ANS✅✅The
non-template duplex does not base pair with the damaged duplex.
Which of the following E. coli proteins is specifically required for duplex invasion by single strand
DNA in the process of homology-directed repair? - ANS✅✅RecA
Bacterial recombination involves a complex called RecBCD. What role does RecBCD play in
homology-directed repair (HDR)? - ANS✅✅RecBCD binds at double-strand break in the DNA then
moves toward the chi site. When it reaches chi, it cleaves one strand of the DNA.
NHEJ usually occurs: - ANS✅✅in nondividing cells.
During recombination single-strand invasion occurs __________. - ANS✅✅when a free 3' end
invades a region of a homologous duplex.
Yeast mating type switch typically begins with: - ANS✅✅A double strand break made at the MAT
locus by HO endonuclease.
Which of the following describes the activity of the bacterial RecA protein? - ANS✅✅coats single-
stranded DNA and catalyzes homologous strand invasion
, Which of the following systems repair double-stranded breaks in the DNA? - ANS✅✅both
homology-directed repair and NHEJ
When is gene conversion least likely to occur? - ANS✅✅G2
What are the two major strategies for double-stranded break repair? - ANS✅✅NHEJ, homology-
directed repair
Which of the following statements correctly describes why unintended double strand breaks can be
severely damaging? - ANS✅✅There is no intact complementary strand to use as a template for
repair
In homology-directed repair, the process of single stranded damaged DNA inserting itself into a
complementary strand of unbroken DNA is called ________. - ANS✅✅strand invasion
What happens at chi sites during homology-directed repair that is mediated by RecBCD enzyme in E.
coli? - ANS✅✅This is the site where RecD nuclease activity is changed.
In Saccharomyces cerevisiae, the proteins RAD51 and DMC1 are the homologs of _____ -
ANS✅✅RecA of E. coli
What is the role of RuvC? - ANS✅✅RuvC is an endonuclease that resolves Holliday junctions
Which of the following is true when comparing homologous recombination to homology-directed
repair (HDR)? - ANS✅✅HDR is used to repair collapsed forks, while homologous recombination is
not
Which statement is FALSE regarding meiotic homologous recombination? - ANS✅✅In meiotic
homologous recombination, the invading strand acts a primer for new DNA synthesis without
extensive heteroduplex formation and the newly synthesized DNA unwinds from the template
strand to pair with the other broken end.
Which protein(s) promote branch migration of Holliday junctions in bacteria? - ANS✅✅RuvAB
and answers graded A+
RecA protein is required for: - ANS✅✅Recombination (repair) and SOS repair
When is homology-directed repair (HDR) most likely to be mutagenic (least likely to exactly replace
missing sequence)? - ANS✅✅During G1, because repair template is usually a homologous
chromosome
__________ make up the heterodimer that recognizes broken DNA ends. - ANS✅✅Ku70 and Ku80
The D-loop is the structure formed when a single-stranded overhang invades the duplex of the repair
template (strand invasion). Which of the following is TRUE regarding strand invasion: - ANS✅✅The
non-template duplex does not base pair with the damaged duplex.
Which of the following E. coli proteins is specifically required for duplex invasion by single strand
DNA in the process of homology-directed repair? - ANS✅✅RecA
Bacterial recombination involves a complex called RecBCD. What role does RecBCD play in
homology-directed repair (HDR)? - ANS✅✅RecBCD binds at double-strand break in the DNA then
moves toward the chi site. When it reaches chi, it cleaves one strand of the DNA.
NHEJ usually occurs: - ANS✅✅in nondividing cells.
During recombination single-strand invasion occurs __________. - ANS✅✅when a free 3' end
invades a region of a homologous duplex.
Yeast mating type switch typically begins with: - ANS✅✅A double strand break made at the MAT
locus by HO endonuclease.
Which of the following describes the activity of the bacterial RecA protein? - ANS✅✅coats single-
stranded DNA and catalyzes homologous strand invasion
, Which of the following systems repair double-stranded breaks in the DNA? - ANS✅✅both
homology-directed repair and NHEJ
When is gene conversion least likely to occur? - ANS✅✅G2
What are the two major strategies for double-stranded break repair? - ANS✅✅NHEJ, homology-
directed repair
Which of the following statements correctly describes why unintended double strand breaks can be
severely damaging? - ANS✅✅There is no intact complementary strand to use as a template for
repair
In homology-directed repair, the process of single stranded damaged DNA inserting itself into a
complementary strand of unbroken DNA is called ________. - ANS✅✅strand invasion
What happens at chi sites during homology-directed repair that is mediated by RecBCD enzyme in E.
coli? - ANS✅✅This is the site where RecD nuclease activity is changed.
In Saccharomyces cerevisiae, the proteins RAD51 and DMC1 are the homologs of _____ -
ANS✅✅RecA of E. coli
What is the role of RuvC? - ANS✅✅RuvC is an endonuclease that resolves Holliday junctions
Which of the following is true when comparing homologous recombination to homology-directed
repair (HDR)? - ANS✅✅HDR is used to repair collapsed forks, while homologous recombination is
not
Which statement is FALSE regarding meiotic homologous recombination? - ANS✅✅In meiotic
homologous recombination, the invading strand acts a primer for new DNA synthesis without
extensive heteroduplex formation and the newly synthesized DNA unwinds from the template
strand to pair with the other broken end.
Which protein(s) promote branch migration of Holliday junctions in bacteria? - ANS✅✅RuvAB
