to freeze whole male mice

Posted at 11:46, 16.8.2006

Descendents of the woolly mammoth could once more walk the earth, new research suggests. Scientists have found that frozen sperm taken from dead animals can be used to produce offspring. If they could also get sperm from animals that have spent millions of years encased in ice, it might even be possible to create a modern-day version of once-extinct species. In the case of the woolly mammoth - several of which have been found preserved in ice - this would mean impregnating its closest living relative, a female Indian elephant, to produce new offspring. Fertility clinics already routinely freeze sperm to create embryos; however it has to be carefully stored to ensure that it does not degrade over time. It is possible instead simply to freeze whole male mice, or their reproductive organs, and use the sperm extracted from them to produce healthy babies. In one test, sperm were retrieved from the bodies of mice that had been kept frozen at minus 20C for 15 years. In other experiments the team found they were able to create healthy offspring using sperm extracted from frozen tests. The study involved no hi-tech freezing procedures. It was not known how long viable sperm could be frozen in animal bodies. But the findings raised the intriguing prospect of resurrecting extinct animals that had remained frozen since the ice age. If spermatozoa of extinct mammalian species (woolly mammoth) can be retrieved from animal bodies that were kept frozen for millions of years in permanent frost, live animals might be restored by injecting them into oocytes (eggs) from females of closely related species. Equally if a valuable animal died unexpectedly, their owners could simply freeze them and later extract sperm to allow them to father offspring after their death. It is not the first time that scientists have contemplated the idea of bringing woolly mammoths back to life. A Canadian and American team used remains of a mammoth found in the Siberian permafrost to map out part of the genetic code of the creatures, that stood 11ft tall and weighed seven tons. They had managed to decode one per cent of the genome - 30million letters of the DNA extracted from a 27,000-year-old mammoth - in a few hours and should be able to complete the entire genome within around a year. Their work made it 'theoretically possible' to recreate species such as the woolly mammoth which became extinct some 10,000 years ago. However they admitted they do not yet know how to do it.