BIO 218 Chapter 13: Bio 218 Ch 13 HW Wk 9_Wi2016_Student
7 Aug 2016
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Light energy used to cleave crosslink: base excision repair endonucle. A dna repair endonuclease or endonuclease-containing complex recognizes, binds to, and excised the damaged base or bases. A dna polymerase fills in the gap, using the undamaged complementary strand of dna as a template. Dna ligase seals the break left by dna polymerase. Prokaryotes and eukaryotes: removes abnormal or chemically modified bases. Specific glycosylases recognize specific base alterations: glycosylases mediated base removal (ap site created, ap endonuclease and phosphodiesterase removes backbone, dna polymerase adds new base, dna ligase reforms phosphodiester bond, nucelotide excision repair . Removes large base defects, e. g. thymine dimers, large alkylated bases, etc. Exinuclease cuts on either side of defect and excises large piece. Exi- not exo- or endo: coli mechanism uvr genes (uv repair, uvr a & b bind to defect, atp dependent bending of damaged dna site by uvr a/b, uvra release, uvrc binds. Uvrc cuts 8th phosphodiester bond 5" of defect.
