Please be aware that the following excerpt references cancer cells and mortality. It also reveals a scientific plot point in the book.

“Scientists knew from studying HeLa that cancer cells could divide indefinitely, and they’d speculated for years about whether cancer was caused by an error in the mechanism that made cells die when they reached their Hayflick [splitting and reproducing] Limit. They also knew that there was a string of DNA at the end of each chromosome called a telomere, which shortened a tiny bit each time a cell divided, like time ticking off a clock. As normal cells go through life, their telomeres shorten with each division until they’re almost gone. They then stop dividing and begin to die. This process correlates with the age of a person: the older we are, the shorter our telomeres, and the fewer times our cells have left to divide before they die.

By the early nineties, a scientist at Yale had used HeLa to discover that human cancer cells contain an enzyme called telomerase that rebuilds telomeres. The presence of telomerase meant cells could keep regenerating their telomeres indefinitely. This explained the mechanics of HeLa’s immortality: telomerase constantly rewound the ticking clock at the end of Henrietta’s chromosomes so they never grew old and never died. It was this immortality, and the strength with which Henrietta’s cells grew, that made it possible for HeLa to take over so many other cultures–they simply outlived and outgrew any other cells they encountered.” –pp 217

This was a great book about persistence, trust, the ethics of human subject research, whistle-blowing, international medical collaboration, relationships, love, loss, the vulnerable position of black women and of children, racism, the relationships of institutions-individuals-communities, economic development, personal and intellectual property rights, and so much more.