In this course, we will discuss the sources of DNA damage and how cells sense and respond to DNA lesions. Multiple DNA repair pathways, their discovery histories and new technologies for measuring DNA damages and repair will be covered in the lectures. Our genome integrity is maintained by a multitude of DNA repair and DNA damage response mechanisms. The failure of these mechanisms can result in a variety of diseases including cancer. The application of DNA damage and repair in therapeutic intervention in cancer and genome editing will be also introduced.