RESUMEN
Estimation of genetic instability by direct quantitation of DNA damage and repair is an important aspect in biomonitoring an individual's risk to cancer. Single cell gel electrophoresis (SCGE) assay or comet assay was carried out on breast cancer patients, their first degree relatives, and controls for the first time for evaluating the basal DNA damage, individual’s susceptibility towards mutagen and repair efficiency. The mean DNA damage in untreated, treated and repaired leucocytes increased significantly from controls to cancer patients. First degree relatives of breast cancer patients showed a significantly higher mean DNA damage than the control group but lesser damage when compared to cancer patients. Among the breast cancer family members, the females showing a relatively high mean DNA damage in untreated, treated and repaired leucocytes, as well as having highly damaged individual cells would be considered as carrying the predisposing factors for cancer development.