Fourth-generation pig cloned in Japan

A Japanese geneticist said Wednesday his research team created the world's first fourth-generation cloned pig, an achievement that could help scientists in medical and other research.

The male pig was born at Tokyo's Meiji University in July, said Hiroshi Nagashima, the geneticist at the university who led the project.

Earlier attempts to clone animals for several generations were problematic. Scientists had thought that was because the genetic material in the nucleus of the donor cell degraded with each successive generation, Nagashima said.

But the team's findings show that a large mammal can be cloned for multiple generations _ in this case, the clone of a clone of a clone of a clone _ without degradation, he said, while acknowledging that mice have already been successively cloned for multiple generations.

Akira Onishi, a geneticist with the government-affiliated Agriculture, Forestry and Fisheries Research Council, said Nagashima's animal could be the world's first fourth-generation cloned pig, an achievement that could help other cloning researchers.

"I am not aware of any other cases," said Onishi, a member of the team that produced Japan's first cloned pig.

"The cloning success rate has been rather low until now, regardless of species," Onishi said. "Researchers have been trying to improve efficiency, but there hasn't been any real progress. We've needed to see this problem resolved."

The results may prove important to breeders of other large animals, such as racehorses or bulls, looking for ways to keep a prized animal in the gene pool, Onishi said.