Cloning Of Animals Widely Duplicated

Cows, sheep, pigs and monkeys in research laboratories around the United States and Europe are now pregnant with clones created by methods similar to those used to make Dolly the sheep, scientists reported at a two-day meeting that ended Friday.

At least one of the pregnant sheep is carrying a clone that has been endowed with an added gene, marking a significant step toward a goal of cloning animals that produce medically useful drugs in their milk.

But many other pregnancies involving clones have already ended in miscarriages, scientists said. And evidence is cropping up that many cloned fetuses have subtle genetic alterations that affect their development in mysterious ways.