GENETICS- MUTATIONS-repair mechanisms

NUCLEOTIDE EXCISION REPAIR 1)USED WHEN? 2) HOW DOES IT WORK?

1) when there are bulky adducts 2) UVR-(A/B/C/D) remove damages DNA segment and DNA polymerase and ligase and seal the single stranded gap.

RECOMBINATION MEDIATED REPAIR 1)USED WHEN? 2) HOW DOES IT WORK?

1) used when there is a larger single-stranded gap, such as in UV radiation damage 2) RecA protein binds to the single-stranded gap. The single-stranded region invades and essentially steals the other strand via recombination

SOS REPAIR 1)USED WHEN? 2) HOW DOES IT WORK?

1) when the DNA is very damaged 2) operates using a specialized bypass polymerase, pol V, that lacks proofreading capability. The RecA protein in the DNA-RecA-SSB complex is an active form that also activates transcription of several genes, including pol V

NUCLEOTIDE BASE EXCISION REPAIR 1)USED WHEN? 2) HOW DOES IT WORK?

1) when there is a modified base 2) 4 steps: glycolyase removes base. endonuclease removes nucleotide. DNA polymerase adds complementary nucleotide. DNA ligase binds new nucleotide to the DNA sequence. REMEMBER: 4 steps: NBER-GEDL.

ALKYLTRANSFERASE 1)USED WHEN? 2) HOW DOES IT WORK?

1) when there is an alkyl group 2)Remove the alkyl group from nucleotides to itself (this inactivates the alkyltransferase)

NONHOMOLOGOUS END JOINING 1)USED WHEN? 2) HOW DOES IT WORK?

1)Double-stranded break that occurs during G1 2) Ku80 and Ku70 bind to DNA ends and trim and ligase reconnects the new ends. loss of DNA occurs

SYNTHESIS DEPENDENT STRAND ANNEALING 1)USED WHEN? 2) HOW DOES IT WORK?

1)Double-stranded break, if DNA is already synthesized 2) ligase digest portions of the broken strand, replication fork is formed in the good strand with the bad sister chromatid invading.

MISMATCH REPAIR 1)USED WHEN? 2) HOW DOES IT WORK?

1)used when there is a base pair mismatch 2)complex of Mut repair proteins excise the nucleotides on the newly synthesized strand, assuming this is the one that caused the mismatch REMEMBER: Mis-mut

P53 REPAIR PATHWAY 1)USED WHEN? 2) HOW DOES IT WORK?

1)when DNA is too damaged2) produces p21(can no longer regulare cell cycle progression-pause) or BAX (can no longer inhibit apoptosis- apoptosis)

PHOTOLYASE 1)USED WHEN? 2) HOW DOES IT WORK?

1)when there are pyrimidine dimers 2) photolyase binds the pyrimidine dimer, visible light energized photolyase and breaks the pyrimidine dimer bonds

DOUBLE STRANDED DNA BREAK 1)USED WHEN? 2) HOW DOES IT WORK?

TWO KINDS! Nonhomologous end joining synthesis dependent strand annealing