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Mammalian Genetics BCH5413 Exam 4
Questions And Answers |Latest 2025 |
Guaranteed Pass
DNA can be both replicated and transcribed into mRNA, which can be translated into protein -
Answer✔What is the central dogma of molecular biology?
True (this is due to intrastrand crosslinking, in which adjacent nucleotides basepair, causing
bubbling) - Answer✔T/F: the addition of bulky aromatic rings and/or exposure to UV light can
cause the DNA to "bubble."
True - Answer✔T/F: chemotherapy can cause both single and double-stranded breaks in DNA.
Damaged DNA can lead to incorrect base pairing, which can lead to mutations (permanent
changes in the DNA sequence) - Answer✔Why is it very important that damaged DNA is
repaired?
Guanine with a new -C=O bond in place of the original =C-H2 bond - Answer✔What is 8-
oxyguanine?
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 - Answer✔What happens to GC base
pairing when guanine is converted to 8-oxyguanine?
1|Page
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2 (instead of guanine's normal 3) - Answer✔How many hydrogen bonds does 8-oxyguanine
have with its partner nucleotide?
An agent used in chemotherapy that has lots of bulky side chains - Answer✔What is cisplatin?
Bulky adducts (DNA "bubbles") caused by the addition of large sidechains and/or intrastrand
crosslinking caused by cisplatin binding to 2 adjacent guanines - Answer✔What type of DNA
damage can be caused by cisplatin?
The addition of cisplatin causes damage to DNA, so introducing it to cancer cells can help
damage/kill them - Answer✔Why is cisplatin an effective treatment for cancer?
Silent mutation - Answer✔What type of mutation occurs when a single basepair is changed, but
the amino acid stays the same?
Missense mutation - Answer✔What type of mutation occurs when a single basepair is changed,
changing the amino acid?
Nonsense mutation - Answer✔What type of mutation occurs when a single basepair is
changed, causing the formation of a stop codon?
False (mutations in the active site are more detrimental than mutations in outer regions of the
protein) - Answer✔T/F: mutations in any part of a protein's sequence can be equally damaging.
Frameshift mutation - Answer✔What type of mutation occurs when a single basepair is
inserted or deleted?
A single-stranded break in the DNA - Answer✔What kind of DNA damage is recognized by the
BER repair proteins?
2|Page
, ©FYNDLAY 2025 ALL RIGHTS RESERVED 11:49 AM A+
Each type of glycosylase recognizes a different type of DNA damage - Answer✔Why is it
necessary to have multiple types of glycosylases?
Mono-functional glycosylases will only cleave an incorrect base; bi-functional glycosylases will
cleave both an incorrect base and the DNA's backbone - Answer✔How does BER differ if a
mono-functional vs. a bi-functional glycosylase is used?
False ("short-patch" DNA repair is when only 1 base is removed and replaced) - Answer✔T/F:
"Short-patch" DNA repair refers to multiple bases being removed and replaced along a short
section of DNA.
FEN1 (cleaves the "flap" of incorrect bases) - Answer✔What is the additional enzyme that's
required for "long-patch" DNA repair before ligase can seal up the nick?
(1) To cut the DNA backbone at the 5' end; (2) to proofread for mistakes by DNAP-beta -
Answer✔What are the 2 functions of APE1?
No ligase has been added, so the fragments are not able to be connected, giving the short band
only (21 bp) - Answer✔Functions of APE1 experiment: why is only 1 short band visible in the
control lane?
DNA ligase is added, causing the 2 fragments to be connected and be located higher on the gel
(40 bp) - Answer✔Functions of APE1 experiment: how does the short band become a long band
(21 bp -> 40 bp)?
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) - Answer✔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?
3|Page
, ©FYNDLAY 2025 ALL RIGHTS RESERVED 11:49 AM A+
DNAP-beta is not able to remove the incorrect base pair before replacing it, as it requires APE1
to do so - Answer✔Functions of APE1 experiment: why does the addition of DNAP-beta in lane
9 not improve the efficiency of forming the long band?
APE1 is able to remove the mismatched base pair, allowing DNAP-beta to easily add a new base
and ligase to seal the nick - Answer✔Functions of APE1 experiment: why does the addition of
APE1 in lane 10 improve the efficiency of long band formation?
True (ligation efficiency is dependent on APE1 concentration) - Answer✔T/F: the more APE1
added to nicked DNA, the more efficient the ligation is.
False (APE1 is required for efficient ligation) - Answer✔T/F: ligation after DNA repair can be
efficient without APE1 (only with ligase and DNAP-beta).
Since glycosylases target many different types of DNA damage, having certain ones be defective
can result in many different consequences - Answer✔Why are there a wide variety of
consequences if BER enzymes are defective?
Bulky adducts in DNA ("bubbles" caused by intrastrand crosslinking) - Answer✔What kind of
DNA damage is recognized by the NER repair proteins?
GG-NER is for inactive genes while TC-NER is for genes being actively transcribed -
Answer✔What is the basic difference between the GG-NER pathway and the TC-NER pathway?
False (oligonucleotide excision involves a long piece of damaged DNA being removed, while
"long-patch" DNA repair involves only removing a few bases) - Answer✔T/F: oligonucleotide
excision is the same as "long-patch" DNA repair.
It uses its beta-sheet "finger" to flip the 2 correct bases (across from the dimerized bases) out
of the helix, allowing it to stabilize and act as a scaffold for other proteins - Answer✔GG-NER:
how does XPC become stabilized at typical DNA damage by bulky adducts?
4|Page
Mammalian Genetics BCH5413 Exam 4
Questions And Answers |Latest 2025 |
Guaranteed Pass
DNA can be both replicated and transcribed into mRNA, which can be translated into protein -
Answer✔What is the central dogma of molecular biology?
True (this is due to intrastrand crosslinking, in which adjacent nucleotides basepair, causing
bubbling) - Answer✔T/F: the addition of bulky aromatic rings and/or exposure to UV light can
cause the DNA to "bubble."
True - Answer✔T/F: chemotherapy can cause both single and double-stranded breaks in DNA.
Damaged DNA can lead to incorrect base pairing, which can lead to mutations (permanent
changes in the DNA sequence) - Answer✔Why is it very important that damaged DNA is
repaired?
Guanine with a new -C=O bond in place of the original =C-H2 bond - Answer✔What is 8-
oxyguanine?
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 - Answer✔What happens to GC base
pairing when guanine is converted to 8-oxyguanine?
1|Page
, ©FYNDLAY 2025 ALL RIGHTS RESERVED 11:49 AM A+
2 (instead of guanine's normal 3) - Answer✔How many hydrogen bonds does 8-oxyguanine
have with its partner nucleotide?
An agent used in chemotherapy that has lots of bulky side chains - Answer✔What is cisplatin?
Bulky adducts (DNA "bubbles") caused by the addition of large sidechains and/or intrastrand
crosslinking caused by cisplatin binding to 2 adjacent guanines - Answer✔What type of DNA
damage can be caused by cisplatin?
The addition of cisplatin causes damage to DNA, so introducing it to cancer cells can help
damage/kill them - Answer✔Why is cisplatin an effective treatment for cancer?
Silent mutation - Answer✔What type of mutation occurs when a single basepair is changed, but
the amino acid stays the same?
Missense mutation - Answer✔What type of mutation occurs when a single basepair is changed,
changing the amino acid?
Nonsense mutation - Answer✔What type of mutation occurs when a single basepair is
changed, causing the formation of a stop codon?
False (mutations in the active site are more detrimental than mutations in outer regions of the
protein) - Answer✔T/F: mutations in any part of a protein's sequence can be equally damaging.
Frameshift mutation - Answer✔What type of mutation occurs when a single basepair is
inserted or deleted?
A single-stranded break in the DNA - Answer✔What kind of DNA damage is recognized by the
BER repair proteins?
2|Page
, ©FYNDLAY 2025 ALL RIGHTS RESERVED 11:49 AM A+
Each type of glycosylase recognizes a different type of DNA damage - Answer✔Why is it
necessary to have multiple types of glycosylases?
Mono-functional glycosylases will only cleave an incorrect base; bi-functional glycosylases will
cleave both an incorrect base and the DNA's backbone - Answer✔How does BER differ if a
mono-functional vs. a bi-functional glycosylase is used?
False ("short-patch" DNA repair is when only 1 base is removed and replaced) - Answer✔T/F:
"Short-patch" DNA repair refers to multiple bases being removed and replaced along a short
section of DNA.
FEN1 (cleaves the "flap" of incorrect bases) - Answer✔What is the additional enzyme that's
required for "long-patch" DNA repair before ligase can seal up the nick?
(1) To cut the DNA backbone at the 5' end; (2) to proofread for mistakes by DNAP-beta -
Answer✔What are the 2 functions of APE1?
No ligase has been added, so the fragments are not able to be connected, giving the short band
only (21 bp) - Answer✔Functions of APE1 experiment: why is only 1 short band visible in the
control lane?
DNA ligase is added, causing the 2 fragments to be connected and be located higher on the gel
(40 bp) - Answer✔Functions of APE1 experiment: how does the short band become a long band
(21 bp -> 40 bp)?
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) - Answer✔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?
3|Page
, ©FYNDLAY 2025 ALL RIGHTS RESERVED 11:49 AM A+
DNAP-beta is not able to remove the incorrect base pair before replacing it, as it requires APE1
to do so - Answer✔Functions of APE1 experiment: why does the addition of DNAP-beta in lane
9 not improve the efficiency of forming the long band?
APE1 is able to remove the mismatched base pair, allowing DNAP-beta to easily add a new base
and ligase to seal the nick - Answer✔Functions of APE1 experiment: why does the addition of
APE1 in lane 10 improve the efficiency of long band formation?
True (ligation efficiency is dependent on APE1 concentration) - Answer✔T/F: the more APE1
added to nicked DNA, the more efficient the ligation is.
False (APE1 is required for efficient ligation) - Answer✔T/F: ligation after DNA repair can be
efficient without APE1 (only with ligase and DNAP-beta).
Since glycosylases target many different types of DNA damage, having certain ones be defective
can result in many different consequences - Answer✔Why are there a wide variety of
consequences if BER enzymes are defective?
Bulky adducts in DNA ("bubbles" caused by intrastrand crosslinking) - Answer✔What kind of
DNA damage is recognized by the NER repair proteins?
GG-NER is for inactive genes while TC-NER is for genes being actively transcribed -
Answer✔What is the basic difference between the GG-NER pathway and the TC-NER pathway?
False (oligonucleotide excision involves a long piece of damaged DNA being removed, while
"long-patch" DNA repair involves only removing a few bases) - Answer✔T/F: oligonucleotide
excision is the same as "long-patch" DNA repair.
It uses its beta-sheet "finger" to flip the 2 correct bases (across from the dimerized bases) out
of the helix, allowing it to stabilize and act as a scaffold for other proteins - Answer✔GG-NER:
how does XPC become stabilized at typical DNA damage by bulky adducts?
4|Page
