Please note: This is a companion version & not the original book. Sample Book Insights: #1 We all sense the finiteness of life, and we all fantasize about living forever. We are enthralled by anti-aging medicine, which tells us that we can stop or even turn back the clock. #2 The Hayflick limit is the number of times a cell can divide before it dies. It varies from species to species, and often correlates with life span. Human cells have a Hayflick limit of about 50 cell divisions, while HeLa cells can divide indefinitely. #3 The saga of Henrietta Lacks raises uncomfortable ethical and social questions, because she never gave informed consent for her cells to be used in this way. But that is another story. #4 The telomere is a region of DNA that ends each chromosome. It is the limit of how many times a cell can duplicate itself, and it is the reason why we age and die. The discovery of telomeres and their possible relationship with the maximum life span of organisms has been one of the most important advances in the fields of genetics and biogerontology.