Your author decided to write this book about DNA Chemistry after being invited to a Caltech Associates dinner to hear a speech by Professor Jacqueline Barton, a leader in the study of chemistry of DNA by the Chemistry and Chemical Engineering Department at Caltech where she is Chair of that department. I have included in this book research I discovered taking place after investigating the Internet. As Professor Barton stated in her Associates lecture, DNA can be damaged in the double helical DNA. She and her Caltech research associates are using a base of sensors they design to find where the DNA is damaged and is in need of repair to avoid cancerous mutations. The purpose of this book is to use the Internet to explore what is happening in DNA Chemistry Research. I find much research is taking place and it is exciting to find out about the impact on Human Health in the areas of Cancer and Alzheimer's Disease. We examine in detail what is happening in the areas of DNA damage detection and what is being done to repair the damage.