Mammalian Genetics BCH5413 Exam 4 Questions and Answers | Verified | 2026

Mammalian Genetics BCH5413 Exam 4 Questions and Answers | Verified | 2026 DNA can be both replicated and transcribed into mRNA, which can be translated into protein - answerWhat 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? 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? 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: "Shortpatch" 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? 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).