What happens when you clone mice for 20 years straight?

This story begins in 1997, the same year I was born. An up-and-coming postdoc at the University of Hawaii, Dr. Teruhiko Wakayama, had just succeeded in creating the first cloned mouse, Cumulina. This was just a year after the birth of Dolly the Sheep, and cloning was still cutting-edge technology. By taking an adult mouse cell and injecting it into an enucleated egg, then stimulating the egg to divide, Dr. Wakayama was able to make a mouse that was the genetic copy of the original cell.By 2005, ...