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vete Non homologous end Soming is present throughout the cell cycle but is particularly common G1 phases whereas HDR predominates in the 5 and 12 phases when a homloy sister druand as a template for repair ed as an emergency solution to the repair of double strand breas In this process broken andre and rejoined by DNA ligation generally with the loss of one or more nucleotides at the site of ge in this process is the recognition of the broken ends by a heterodimer Ku70 and usu pro pendent protein kinase DNA PK to act Phosphorylation by this kinase trggers recruitment of end actors including the nuclease Artemis that trim the DNA ends making the compatible for gation s both endo and exonuclease activities and trims the ONA ends The final joining of double strand ed out by the DNA ligase IV in association with XRCC4 A Non Homologous End Joining Double strand break Ku70 Ku80 heterodimer DNA PK Artemis XRCCA and DNA ligase IV Error prone repair Ertion or deletion i e indel mutations B Himology Directed Repair Homologous template D x Error free DNA repair 124 A Non homologaus end joining NHEI is a homology independent repair pathway that is initiated by g of Ku70 Ku80 heterodimers to the broken DNA ends Ku70 KUBo heterodimer binds to ONA ends with high Cu then recruits the Ser The kinase DNA PK DNA dependent protein kinase to phosphorylate a number of am targets including the terminal end processing enzyme Artemis that cleaves single stranded avemangs ligase IV and the scaffold protein XRCC4 which catalyse the ligation of DNA ends B Homology directed repair a process of homologous recombination where a DNA template is used to provide the homology necessary e repair of a double strand break DSB ene conversion and repair of DNA may lead to the replacement of one allele by another This phenomenon is known as on It is a byproduct of the recombinational repair mechanism It involves homologous recombination ted by DNA double strand break Gene conversion mediates the unidirectional transfer of genetic om a donor sequence to a highly homologous acceptor Most gene conversion is derived from the air of the heteroduplex DNA that is formed between the donor and acceptor DNA sequences f gene conversion from heteroduplex DNA As we have discussed in the case of a double strand of homologous recombination recombination forms hybrid heteroduplex DNA malecules with two y strands from different DNA If the two strands in a heteroduplex come from chromosomes with s there will be a mismatch of bases in the heteroduplex DNA The mismatch correction probably the resolution of the double Holliday junctions It is the broken strand that is usually corrected using

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