6 DNA damage, repair, and mutations Flashcards

Question

what are sometypes of chemical and physical mutations

Answer 1

Chemical - alkylating agents - reactive oxygen species - intercalating agents - Base analogs Physical - UV/Ionizing radiation

Answer 2

○ Covalently links neighbouring pyrimidines ○ Stops replication ○ Results in transition mutations

Answer 3

○ "lightning bolts hitting DNA" - Likely to cause actual breaks in DNA

Answer 4

addition of alkyl grp to a nucleotide - disrupts correct base pairing

Answer 5

Chemically similar to ATCG(imposter) - can be incorrectly incorporated into DNA polymerase

Answer 6

Inserts between base pairs - distorts dbl helix - increases slippage

Answer 7

○ Nucleotide been removed and theres jus a hole in the DNA

Answer 8

NON-BULKY - alkylation - oxidation - deamination - depurination BULKY - pyrimidine dimer - bulky adduct - base mismatch - loop - dbl strand break

Answer 9

WT that have been mutants and are now WT again

Answer 10

total # revertants / # spontaneous revertants

Answer 11

Base excision repair

Answer 12

Nucleotide excision repair - (pyrimidine dimmer can also be fixed by direct repair)

Answer 13

base mismatch and loop

Answer 14

double stranded break

Answer 15

- surveillance(detect errors) - Excision (Find mistake and cut it out) - polymerization (replace what was cut) - strand ligation (reconnect bonds in repaired stand)

Answer 16

○ Some errors can be reverted by using specific enzymes because they happen so often

Answer 17

○ One of the simplest way to repair ○ Detection and excision § Enzyme removes the whole error § Cut strand with endonuclease to allow DNA entry to fix § Polymerase replaces error with correct base § Can replace 1 base or a whole chunk

Answer 18

For larger damage that affects multiple base pairs § Damage detection □ Global genome surveillance finds □ Look for stalled RNA polymerase § Strand separation □ Helicase opens DNA § excision □ Endonuclease cuts out whole chunk § Polymerization □ Polymerase fixes § Ligation □ Glued back together by DNA ligase

Answer 19

○ Uses concept of DNA methylation ○ Detection § Template strand has a methyl group and new strand doesn’t so we know which one is right

Answer 20

○ Most serious of damage ○ Affects both strands so theres no template

Answer 21

homologous recombination (HR), non homologous End Joining (NHEJ)

Answer 22

§ Uses homo chromos as template § Active post DNA replication § More error proof

Answer 23

§ DNA strands join independent of complementarity § Active in dividing and non dividing cells § Doesn’t req template strand § More prone to errors § DNA strands jus glued together

Answer 24

○ Detection § Proteins bind to end to supress further damage ○ Strand resection § Recruit of kinase and nuclease proteins to make blunt ends ○ Polymerization § Polymerase fills end for ligation (sticky ends) § Does not add bases (no template) ○ Ligation § Ligates the 2 sticky ends together

Answer 25

○ Detection § Same way NHEJ ○ Strand resection § Cuts back from break § Creates 3' overhangs (sticky ends) ○ Strand exchange/invastion § Seperates double stranded DNA § Forms a Displacement loop (D-Loop) ○ Polymerization § Missing DNA copied from template ○ 2 complex pathways from here § Synthesis dependant strand annealing pathway (SDSA) § Double strand break repair pathway (DSBR)

Answer 26

- both strands broken - One broken strand "invades" a matching DNA strand to use as template. - The broken strand copies the missing DNA using the intact strand as guide. - The newly made DNA strand separates and sticks back to its original partner strand. - No Crossing-Over: Unlike other repair methods, SDSA does not swap large sections of DNA between chromosomes, avoiding genetic changes.

Answer 27

It’s like repairing a torn rope by using a similar rope to guide the fix, but sometimes parts of the ropes get exchanged.

Answer 28

Direct repair - uses enzymes

6 DNA damage, repair, and mutations Flashcards

(56 cards)