In a human cell, normal metabolic activities and environmental factors such as radiation can cause as many as one million individual molecular lesions per day. To maintain genetic integrity and normal cell functions, a mechanism called DNA damage repair is crucial in allowing a cell to identify DNA damage and mediate its repair. DNA repair capacities differ between species and individuals within species. Quantifying this difference is important for research purposes and for clinical diagnostics (e.g. personalized disease prevention, prescribing chemotherapy tailored to an individual patient based on differences in DNA repair capacity of the patient). Furthermore, the different types of DNA damage necessitate different molecular pathways of DNA repair.