A high percentage of cloned monkey embryos that look healthy are really a "gallery of horrors" deep within, says a researcher at Advanced Cell Technology, the company that last month published the first paper on cloned human embryos.
This could mean that there is something unique about primate eggs that will make cloning monkeys or people far more difficult than cloning other animals. At the very least, the experiments show that there's a lot to learn before primates can be cloned.
Tanja Dominko, who presented the results last week at a conference in Washington DC, did the work before joining ACT, while she was working for the reproductive biologist Gerald Schatten at the Oregon Regional Primate Research Center in Beaverton.
Several groups have been trying for years to clone monkeys, but while the embryos look normal, no one has ever got them to develop further.