1|Page
Mammalian Genetics BCH5413 Exam 4 Exam|
Complete Exam Questions and CORRECT Answers|
(2025 update) Assured success| grade A+
What is the central dogma of molecular biology? - (ANSWER)DNA can be both
replicated and transcribed into mRNA, which can be translated into protein
T/F: the addition of bulky aromatic rings and/or exposure to UV light can cause
the DNA to "bubble." - (ANSWER)True (this is due to intrastrand crosslinking, in
which adjacent nucleotides basepair, causing bubbling)
T/F: chemotherapy can cause both single and double-stranded breaks in DNA. -
(ANSWER)True
Why is it very important that damaged DNA is repaired? - (ANSWER)Damaged
DNA can lead to incorrect base pairing, which can lead to mutations (permanent
changes in the DNA sequence)
What is 8-oxyguanine? - (ANSWER)Guanine with a new -C=O bond in place of the
original =C-H2 bond
What happens to GC base pairing when guanine is converted to 8-oxyguanine? -
(ANSWER)8-oxyguanine flips over, causing it to hydrogen bond with adenine
(instead of cytosine) and become a thymine in the next round of DNA replication
How many hydrogen bonds does 8-oxyguanine have with its partner nucleotide? -
(ANSWER)2 (instead of guanine's normal 3)
,2|Page
What is cisplatin? - (ANSWER)An agent used in chemotherapy that has lots of
bulky side chains
What type of DNA damage can be caused by cisplatin? - (ANSWER)Bulky adducts
(DNA "bubbles") caused by the addition of large sidechains and/or intrastrand
crosslinking caused by cisplatin binding to 2 adjacent guanines
Why is cisplatin an effective treatment for cancer? - (ANSWER)The addition of
cisplatin causes damage to DNA, so introducing it to cancer cells can help
damage/kill them
What type of mutation occurs when a single basepair is changed, but the amino
acid stays the same? - (ANSWER)Silent mutation
What type of mutation occurs when a single basepair is changed, changing the
amino acid? - (ANSWER)Missense mutation
What type of mutation occurs when a single basepair is changed, causing the
formation of a stop codon? - (ANSWER)Nonsense mutation
T/F: mutations in any part of a protein's sequence can be equally damaging. -
(ANSWER)False (mutations in the active site are more detrimental than mutations
in outer regions of the protein)
,3|Page
What type of mutation occurs when a single basepair is inserted or deleted? -
(ANSWER)Frameshift mutation
What kind of DNA damage is recognized by the BER repair proteins? - (ANSWER)A
single-stranded break in the DNA
Why is it necessary to have multiple types of glycosylases? - (ANSWER)Each type
of glycosylase recognizes a different type of DNA damage
How does BER differ if a mono-functional vs. a bi-functional glycosylase is used? -
(ANSWER)Mono-functional glycosylases will only cleave an incorrect base; bi-
functional glycosylases will cleave both an incorrect base and the DNA's backbone
T/F: "Short-patch" DNA repair refers to multiple bases being removed and
replaced along a short section of DNA. - (ANSWER)False ("short-patch" DNA
repair is when only 1 base is removed and replaced)
What is the additional enzyme that's required for "long-patch" DNA repair before
ligase can seal up the nick? - (ANSWER)FEN1 (cleaves the "flap" of incorrect
bases)
What are the 2 functions of APE1? - (ANSWER)(1) To cut the DNA backbone at
the 5' end; (2) to proofread for mistakes by DNAP-beta
, 4|Page
Functions of APE1 experiment: why is only 1 short band visible in the control
lane? - (ANSWER)No ligase has been added, so the fragments are not able to be
connected, giving the short band only (21 bp)
Functions of APE1 experiment: how does the short band become a long band (21
bp -> 40 bp)? - (ANSWER)DNA ligase is added, causing the 2 fragments to be
connected and be located higher on the gel (40 bp)
Functions of APE1 experiment: why does adding ligase to lane 3 (correct A/T
pairing) cause robust formation of the long band while adding ligase to lane 8
(G/T mismatch) only results in a small amount of the long band? - (ANSWER)If the
base pairing before a nick is CORRECT, ligase can easily seal it back up; if the base
pairing before a nick is a MISMATCH, ligase requires the help of APE1 and DNAP-
beta to efficiently seal the nick (low efficiency if ligase acts alone)
Functions of APE1 experiment: why does the addition of DNAP-beta in lane 9 not
improve the efficiency of forming the long band? - (ANSWER)DNAP-beta is not
able to remove the incorrect base pair before replacing it, as it requires APE1 to
do so
Functions of APE1 experiment: why does the addition of APE1 in lane 10 improve
the efficiency of long band formation? - (ANSWER)APE1 is able to remove the
mismatched base pair, allowing DNAP-beta to easily add a new base and ligase to
seal the nick
T/F: the more APE1 added to nicked DNA, the more efficient the ligation is. -
(ANSWER)True (ligation efficiency is dependent on APE1 concentration)
Mammalian Genetics BCH5413 Exam 4 Exam|
Complete Exam Questions and CORRECT Answers|
(2025 update) Assured success| grade A+
What is the central dogma of molecular biology? - (ANSWER)DNA can be both
replicated and transcribed into mRNA, which can be translated into protein
T/F: the addition of bulky aromatic rings and/or exposure to UV light can cause
the DNA to "bubble." - (ANSWER)True (this is due to intrastrand crosslinking, in
which adjacent nucleotides basepair, causing bubbling)
T/F: chemotherapy can cause both single and double-stranded breaks in DNA. -
(ANSWER)True
Why is it very important that damaged DNA is repaired? - (ANSWER)Damaged
DNA can lead to incorrect base pairing, which can lead to mutations (permanent
changes in the DNA sequence)
What is 8-oxyguanine? - (ANSWER)Guanine with a new -C=O bond in place of the
original =C-H2 bond
What happens to GC base pairing when guanine is converted to 8-oxyguanine? -
(ANSWER)8-oxyguanine flips over, causing it to hydrogen bond with adenine
(instead of cytosine) and become a thymine in the next round of DNA replication
How many hydrogen bonds does 8-oxyguanine have with its partner nucleotide? -
(ANSWER)2 (instead of guanine's normal 3)
,2|Page
What is cisplatin? - (ANSWER)An agent used in chemotherapy that has lots of
bulky side chains
What type of DNA damage can be caused by cisplatin? - (ANSWER)Bulky adducts
(DNA "bubbles") caused by the addition of large sidechains and/or intrastrand
crosslinking caused by cisplatin binding to 2 adjacent guanines
Why is cisplatin an effective treatment for cancer? - (ANSWER)The addition of
cisplatin causes damage to DNA, so introducing it to cancer cells can help
damage/kill them
What type of mutation occurs when a single basepair is changed, but the amino
acid stays the same? - (ANSWER)Silent mutation
What type of mutation occurs when a single basepair is changed, changing the
amino acid? - (ANSWER)Missense mutation
What type of mutation occurs when a single basepair is changed, causing the
formation of a stop codon? - (ANSWER)Nonsense mutation
T/F: mutations in any part of a protein's sequence can be equally damaging. -
(ANSWER)False (mutations in the active site are more detrimental than mutations
in outer regions of the protein)
,3|Page
What type of mutation occurs when a single basepair is inserted or deleted? -
(ANSWER)Frameshift mutation
What kind of DNA damage is recognized by the BER repair proteins? - (ANSWER)A
single-stranded break in the DNA
Why is it necessary to have multiple types of glycosylases? - (ANSWER)Each type
of glycosylase recognizes a different type of DNA damage
How does BER differ if a mono-functional vs. a bi-functional glycosylase is used? -
(ANSWER)Mono-functional glycosylases will only cleave an incorrect base; bi-
functional glycosylases will cleave both an incorrect base and the DNA's backbone
T/F: "Short-patch" DNA repair refers to multiple bases being removed and
replaced along a short section of DNA. - (ANSWER)False ("short-patch" DNA
repair is when only 1 base is removed and replaced)
What is the additional enzyme that's required for "long-patch" DNA repair before
ligase can seal up the nick? - (ANSWER)FEN1 (cleaves the "flap" of incorrect
bases)
What are the 2 functions of APE1? - (ANSWER)(1) To cut the DNA backbone at
the 5' end; (2) to proofread for mistakes by DNAP-beta
, 4|Page
Functions of APE1 experiment: why is only 1 short band visible in the control
lane? - (ANSWER)No ligase has been added, so the fragments are not able to be
connected, giving the short band only (21 bp)
Functions of APE1 experiment: how does the short band become a long band (21
bp -> 40 bp)? - (ANSWER)DNA ligase is added, causing the 2 fragments to be
connected and be located higher on the gel (40 bp)
Functions of APE1 experiment: why does adding ligase to lane 3 (correct A/T
pairing) cause robust formation of the long band while adding ligase to lane 8
(G/T mismatch) only results in a small amount of the long band? - (ANSWER)If the
base pairing before a nick is CORRECT, ligase can easily seal it back up; if the base
pairing before a nick is a MISMATCH, ligase requires the help of APE1 and DNAP-
beta to efficiently seal the nick (low efficiency if ligase acts alone)
Functions of APE1 experiment: why does the addition of DNAP-beta in lane 9 not
improve the efficiency of forming the long band? - (ANSWER)DNAP-beta is not
able to remove the incorrect base pair before replacing it, as it requires APE1 to
do so
Functions of APE1 experiment: why does the addition of APE1 in lane 10 improve
the efficiency of long band formation? - (ANSWER)APE1 is able to remove the
mismatched base pair, allowing DNAP-beta to easily add a new base and ligase to
seal the nick
T/F: the more APE1 added to nicked DNA, the more efficient the ligation is. -
(ANSWER)True (ligation efficiency is dependent on APE1 concentration)
