DNA molecules undergo chemical reactions which may alter their structure and DNA repair is the process by which such damages are repaired. Significant damage may hinder the RNA transcription process as well as cause mutations in the DNA molecule. Cell aging, apoptosis and cancerous tumors are common outcomes of long-term damage to DNA. Cellular processes such as the stress to reactive oxygen species as well as exposure to ionizing radiation and large amounts of ultraviolet light are sources of DNA damage. This book explores all the important aspects of DNA repair in the present day scenario. Scientists and students actively engaged in this field will find this book full of crucial and unexplored concepts.