It probably doesn't help my own credibility when I keep saying North Korea when it was, in fact, South Korean researchers that did the cloning.
Okay, gotta correct myself here...
Vogel, Science, 2/13/04...
Perhaps the Korean scientists' most important advantage was the whopping 242 eggs they had to work with. The team obtained oocytes and donor cells from 16 healthy women, who underwent hormone treatment to stimulate their ovaries to overproduce maturing eggs. (The women donated specifically for the experiments, were not compensated, and were informed that they would not personally benefit from the research.) "More than 200 eggs? Wow. I'm drooling," says Jose Cibelli of Michigan State University in East Lansing, who is a co-author of the paper but did not take part in the cloning procedures. When he attempted human cloning at the biotech firm Advanced Cell Technology in Worcester, Massachusetts, a few years ago, he says, his team had fewer than 20 usable eggs.
The plentiful eggs gave Moon, Hwang, and colleagues a chance to tweak the methods they used, varying the time between inserting the new nucleus and triggering cell division as well as testing several different kinds of growth media. In the most successful protocol, the scientists were able to get 19 of 66 cloned eggs to develop into blastocysts. That success rate is lower than researchers have reported with mouse and cattle cloning, but "at this stage in the game, it's encouraging," says Ian Wilmut of the Roslin Institute in Midlothian, U.K., who helped lead the team that cloned Dolly.
The team's success in deriving stem cells was lower than that of other researchers, however. Whereas some teams are able to derive ES cells from up to half of their embryos (usually created for in vitro fertilization treatments but no longer needed), Moon and Hwang got just one cell line in 20 tries. The authors suspect that some of the cloned blastocysts might have suffered the chromosomal abnormalities observed in other primate cloning attempts.
So, 242 eggs, quite a few blastocysts (30 in all, 19 out of 66 in the most effective protocol), one successful stem cell line from 20 ICM cells. I misremembered it as one successful clone.
From the writeup (Hwang et al, Science, 2/13/04):
A total of 242 oocytes were obtained from 16 volunteers (there were one or two donors for each trial) after ovarian stimulation: 176 metaphase II (MII) oocytes were used directly for SCNT, whereas the remaining 66 oocytes were allowed to mature to the MII stage before use in SCNT. Autologous SCNT was performed; that is, the donor's own cumulus cell, isolated from the cumulus-oocyte complex (COC), was transferred back into the donor's own enucleated oocyte.
So the nucleus came from the same individual as the egg. Huh.