For the last decade, scientists have cloned from early embryo cells, which are not yet specialized.

First, it is impossible to grow embryo cells in culture without having them change into something that looks like skin cells.

Few embryo cells take up the added genes, and even fewer use them.

They took one of those embryo cells and merged it with a second cow egg whose own nucleus has been removed.

But this time, since it was an embryo cell that was involved, the development was more likely to proceed.

After the animal was born, the scientists could ascertain whether any of the added genes were taken up by the embryo cells.

And if you can do that, is the single embryo cell the moral equivalent of an entire embryo?

For a decade, scientists have been able to clone animals from very early embryo cells.

It seemed to say that mammals could be cloned - at least from embryo cells.

Researchers, however, have not yet cured any disease or even routinely turned embryo cells into specific adult cells.