Teruhiko Wakayama and his colleagues at the Institution Laboratory for Genomic Reprogramming in Japan have reported that they were able to create clones of mice that had been frozen for 16 years. According to U.S. News & World Report:
Wakayama…and his colleagues took brain tissue from a mouse strain frozen at minus 20 degrees Celsius for up to 16 years and transferred the nuclei (containing the genetic material) to empty egg cells.
These two-cell embryos were used to generate embryonic stem cell lines that resulted in 12 healthy cloned mice, which grew into normal adults.
The technique did not require nuclei from an intact donor cell. The cloning efficiency was about the same as using conventional cloning methods, the study authors stated….
Until now, researchers had believed that ice crystals formed in frozen cells would cause irreparable damage to the DNA, making cloning of long-dead animals impossible.
Wakayama told U.S. News that cloning a wooly mammoth from frozen remains from the Arctic tundra is "probably impossible."
Wakayama was apparently a bit more hopeful when he talked with The New Scientist:
The finding also raises hopes of one day being able to resurrect extinct animals frozen in permafrost, such as the woolly mammoth, says Teruhiko Wakayama of the RIKEN Center for Developmental Biology in Kobe, Japan, who led the research. "It would be very difficult, but our work suggests that it is no longer science fiction," he says….
Resurrecting extinct animals would be far trickier. Woolly mammoth carcasses would most likely have frozen and thawed several times over the aeons, which would cause far more damage to the nucleus than a one-off freezing.
Potentially easier would be cloning cryogenically frozen humans, though the consensus among cloning experts is that it would be unethical and dangerous to clone a human. In any case, people who sign up to be cryogenically preserved usually hope to be resuscitated rather than cloned.