A group of Japanese and Chinese researchers has succeeded in cloning two cows using skin cells from a dead cow embryo kept frozen at roughly the same temperature as the Siberian permafrost, a Japanese member of the group said Saturday.
Japanese researchers believe the breakthrough will accelerate their efforts to clone the extinct woolly mammoth, which existed between 1.6 million and 10,000 years ago.
The cloning procedure was carried out at a temperature of minus 35 C for the first time, said Tatsuyuki Suzuki, a professor at Yamaguchi University, adding that fertilized eggs are normally kept frozen at minus 196 C in liquid nitrogen.
Frozen soil in Siberia contains mammoth cells dating back to the Pleistocene era.
The group comprises Suzuki's research team and researchers from Lai Yang Agricultural College in China's Shandong Province, according to Suzuki.
After freezing skin cells from a cow embryo for three months at minus 35 C, the group transplanted the thawed nucleus into a separate unfertilized egg with its nucleus removed, creating a cloning embryo.
The group transplanted the embryos into five cows at Lai Yang college after sending the embryos to China by air in February.
Two of the five cows gave birth to cloned baby cows, on Nov. 3 and 6.
Mammoth experts point out that it would be difficult to find mammoths' somatic cells in good condition, but Suzuki said he may find cells from an embryo if he can find a pregnant mammoth.