AbstractThe RAD51 gene encodes proteins that are important for the repair of double-strand DNA breaks by recombination. Thus, genetic variability in the gene may contribute to the occurrence and progression of breast carcinoma. We investigated the association of polymorphisms in the DNA repair genes RAD51-site 135G/C with the breast cancer risk. Genotypes were determined by PCR-RFLP assays in 55 female patients with breast cancers and 80 age-matched healthy controls. Bloods samples were taken from all the patients and health controls and DNA was isolated. The region of interest was amplified based on PCR. After amplification, we used a restriction enzyme (RAD51; MvaI) and digested the PCR product. Then, these DNA fragments were size separated in gel electrophoresis. We identified changes in the nucleotides in these specific regions and confirmed the genotyping via sequencing a subset of PCR products using an Applied Biosystems Automated Sequencer. We observed that both allele and genotype frequencies significantly differed between breast cancer patients and healthy control. The frequency of variant allele, C, was increased to 0.25 in breast cancer group as opposed to the frequency of 0.125 in control group. Similarly, the genotypes carrying the variant allele C (CC + GC) had an elevated frequency and increased odd’s ratio among breast cancer group. The obtained results indicate that the polymorphism of RAD51 genes may be associated with the incidence of breast cancer in the Eastern Mediterranean region population. We hypothesized that common polymorphisms in DNA repair and cell cycle regulator genes modify DNA repair machinery which contribute to breast cancer susceptibility.