There were good reasons for this belief. Granted, a few stem cells remain scattered here and there in the
adult body. They serve to generate replacements when specialised cells die, for instance blood cells. Stem
cells are able to divide an infinite number of times and can develop into the more specialised cells that need replacing. But no one had ever seen a specialised cell go back to its original form and become a stem cell
again. A plausible explanation for this appeared to be that the genetic information in stem cells – the genetic
code that gives stem cells their special talents – vanishes or becomes irreversibly suppressed when cells
specialise