Several genes were involved in the DNA repair machinery which are 1) Nonhomologous end joining (NHEJ) pathway involved in the G1/S phase, 2) Homologous recombinational repair (HRR) pathway involved in the S/G2 phase. XRCC4, LIG4, MRN and ATM are well known genes involved in the NHEJ pathway, while MRE11, RAD50, NBS1 (MRN), RAD51, XRCC2, XRCC3, RAD51B, RAD51C, RAD 51D, RAD52 or RAD54 are known to be associated with HRR pathway.