As a result of its investigation, the NIH said that to qualify for funding, all proposals for research on human subjects had to be approved by review boards—independent bodies made up of professionals and laypeople of diverse races, classes, and backgrounds—to ensure that they met the NIH’s ethics requirements, including detailed informed consent. Scientists said medical research was doomed. In a letter to the editor of Science, one of them warned, “When we are prevented from attempting seemingly innocuous studies of cancer behavior in humans … we may mark 1966 as the year in which all medical progress ceased.
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. Then they 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 their 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.