**7. XRCC1**

The X-Ray Cross Complementing group I XRCC1 gene belongs to The Base Excision Repair IBER) pathway. The XRCC1 gene product plays an important role in the BER pathway by acting as a scolfold for the other DNA repair proteins, such as DNA polymerase B (Kubota et al., 1996), and DNA ligase III (Caldecott, 2003). Few common single nucleotide polymoprhisms of the XRCC1 gene have been identified at codon 194 (G>T substitution at position 26304, exon 6, Arg to Trp), codon 280 (G>A substitution at position 27466, exon 9, Arg to His) and 399 (G>A substitution at position 28152, exon 10, Arg to Gln). The individuals carrying XRCC1 399 variants have been shown to have higher levels of DNA adduct (Lunn et al., 2000) and to be at greater risk for tobacco related DNA damage (Lei et al., 2002). Few studies reported XRCC1 399AA genotype to be significantly associated with lung cancer risk in Caucasian population (Divine et al., 2001; Zhou et al., 2003), Korean population (Park et al., 2002), and Indian population (Sreeja et al., 2008).
