BCH5413 - Exam 3 QUESTIONS WITH ANSWERS,

BCH5413 - Exam 3 QUESTIONS WITH |\ |\ |\ |\ |\ |\




ANSWERS


What is DNA damage - CORRECT ANSWERS ✔✔a chemical
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alteration to DNA |\ |\




Is DNA continually damaged? - CORRECT ANSWERS ✔✔YES
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- there are 10^4 to 10^6 damaging events in a single human
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cell every day |\ |\




DNA damage can be caused by.. - CORRECT ANSWERS ✔✔-
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spontaneous cleavage of inherently unstable chemical bonds in |\ |\ |\ |\ |\ |\ |\ |\


DNA (eg. deamination and base loss)
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- environmental/external agents (eg. UV, ionizing radiation)
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- endogenous genotoxic chemicals (eg. ROS generated from
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metabolism)


If left unrepaired, DNA damage can lead to.. - CORRECT
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ANSWERS ✔✔mutation |\




A mutation is.. - CORRECT ANSWERS ✔✔a change in the normal
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sequence of DNA |\ |\




If a particular kind of DNA damage is likely to cause a mutation,
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we call it.. - CORRECT ANSWERS ✔✔genotoxic
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,Mutations mostly occur during.. - CORRECT ANSWERS
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✔✔replication
- when a DNA Pol inserts wrong nucleotides as it reads a
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damaged template |\ |\




*on normal templates, the frequency of copying errors by DNA
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pol is low
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Mutation types - CORRECT ANSWERS ✔✔- insertion/deletion
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- point mutations (changes in single base pair)
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Point mutations
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- in protein coding regions
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- outside coding regions - CORRECT ANSWERS ✔✔In protein
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coding regions |\




- nonsense mutation (due to stop codon)
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- missense mutation (AA substitution)
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- silent mutation
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Outside coding regions |\ |\




- mostly without a consequence
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- exceptions: intronic regions affecting splicing, regulatory
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elements

,Mutations may alter gene function, and can cause diseases such
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as ____ (in oncogenes/tumor suppressor genes) - CORRECT
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ANSWERS ✔✔cancer |\




Damage caused by alkylation of bases |\ |\ |\ |\ |\




- alkylation is a process where electrophilic substances... -
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CORRECT ANSWERS ✔✔- seek negative centers in DNA (and
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other molecules) |\




- attack them
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- add carbon-containing groups (alkyl groups)
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Alkylating agents add alkyl groups to... - CORRECT ANSWERS
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✔✔bases


Many ____ are electrophiles that alkylate DNA - CORRECT
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ANSWERS ✔✔carcinogens |\




The most commonly attached targets of alkylation in DNA are... -
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CORRECT ANSWERS ✔✔phosphodiester bonds |\ |\ |\




Do alkylation events change base pairing? - CORRECT ANSWERS
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✔✔SOMETIMES
- some do not and are innocuous (alkylation of guanine N7)
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- some disrupt base pairing (alkylation of adenine N3) and may
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stall DNA replication and thus are cytotoxic (cause mutation if
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cell attempts to replicate without repair)
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, - others alter base pairing properties of a base and are
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mutagenic/genotoxic (alkylation of guanine O6) |\ |\ |\ |\




Damage caused by radiation: UV rays (non-ionizing radiation)
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- energy
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- what it causes - CORRECT ANSWERS ✔✔- comparatively low
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energetic |\




- cross-link adjacent pyrimidines, resulting in formation of
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pyrimidine dimers (CPD's) which distort DNA, disrupt base
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pairing, and block replication or cause replication errors if
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bypassed


Gamma and X-rays |\ |\




- energy
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- what it does
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- what it forms - CORRECT ANSWERS ✔✔- much more energetic
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- ionize molecules around the DNA (eg. water)
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- form highly reactive free radicals that attach DNA and can
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break single or double strands and alter bases (oxidative
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damage)


What are highly reactive free radicals - CORRECT ANSWERS
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✔✔chemical substances with unpaired electron |\ |\ |\ |\




Reversing DNA damage |\ |\