Author: Steve Connor.
Date of Publication: Wednesday, 5 November 2008
http://www.independent.co.uk/news/science/the-big-question-will-scientists-ever-be-able-to-resurrect-longextinct-animals-by-cloning-992019.html
Gabriela Garcia fernandez.
Scientists in Japan have refined a cloning technique that has enabled them to clone mice from the frozen corpse of a mouse that had been kept in a freezer for 16 years at a temperature of -20C. The team was led by Teruhiko Wakayama of the Riken Centre for Developmental Biology in Kobe, Japan. The scientists believe that it might be possible in the future to use the same techniques to clone creatures from the frozen tissue of animals found buried, for example, the frozen corpses of mammoths.
This is not the first time that scientists have produced clones from dead animals. In fact Dolly herself was cloned from a sheep that had died long before. Scientists took tissue from a dead sheep and carefully frozen it using special chemicals called "cryopreservatives". These prevent the formation of damaging ice crystals inside the cells. Dolly was therefore the clone of a frozen animal that had died many years before she was born.
Wakayama and his colleagues pointout that all clones so far produced from dead animals have been created from quick-frozen tissue that has been meticulously kept at very cold temperatures without thawing, using cryopreservation. Scientists declared that this is not possible with dead animals frozen in natural conditions, the cells of tissue will presumably bind strongly to each other and freeze gradually after death due to the large body size. It remains to be shown whether nuclei can be collected from the bodies frozen without cryoprotectants, and whether they will be viable for use in cloning. Scientists have tried with some success to extract DNA from various extinct mammals, such as mammoths and the Tasmanian tiger, but cloning implies a whole set of problems. The first concerns the difficulty of extracting cells with perfectly preserved DNA, since it degrades over time. Corpses frozen for several thousand years are likely to have suffered repeated thawing and freezing that will damage both the cells and their DNA. Another problem is trying to find suitable non-extinct animals to act as surrogate egg donors and mothers.
Some scientists are suggesting this as a last measure to safeguard threatened animals that are difficult to breed in captivity. However, cloning is never going to be the panacea to the threat of extinction. The biggest problems faced by threatened animals are habitat loss, human encroachment on their territories, hunting and climate change. Cloning animals on the verge of extinction could helpspecies to hang on in zoos and parks, but it does little to generate the genetic diversity that is so important for the long-term survival of species. It also does nothing to address the root causes of extinction.
http://www.independent.co.uk/news/science/the-big-question-will-scientists-ever-be-able-to-resurrect-longextinct-animals-by-cloning-992019.html
Gabriela Garcia fernandez.
Scientists in Japan have refined a cloning technique that has enabled them to clone mice from the frozen corpse of a mouse that had been kept in a freezer for 16 years at a temperature of -20C. The team was led by Teruhiko Wakayama of the Riken Centre for Developmental Biology in Kobe, Japan. The scientists believe that it might be possible in the future to use the same techniques to clone creatures from the frozen tissue of animals found buried, for example, the frozen corpses of mammoths.
This is not the first time that scientists have produced clones from dead animals. In fact Dolly herself was cloned from a sheep that had died long before. Scientists took tissue from a dead sheep and carefully frozen it using special chemicals called "cryopreservatives". These prevent the formation of damaging ice crystals inside the cells. Dolly was therefore the clone of a frozen animal that had died many years before she was born.
Wakayama and his colleagues pointout that all clones so far produced from dead animals have been created from quick-frozen tissue that has been meticulously kept at very cold temperatures without thawing, using cryopreservation. Scientists declared that this is not possible with dead animals frozen in natural conditions, the cells of tissue will presumably bind strongly to each other and freeze gradually after death due to the large body size. It remains to be shown whether nuclei can be collected from the bodies frozen without cryoprotectants, and whether they will be viable for use in cloning. Scientists have tried with some success to extract DNA from various extinct mammals, such as mammoths and the Tasmanian tiger, but cloning implies a whole set of problems. The first concerns the difficulty of extracting cells with perfectly preserved DNA, since it degrades over time. Corpses frozen for several thousand years are likely to have suffered repeated thawing and freezing that will damage both the cells and their DNA. Another problem is trying to find suitable non-extinct animals to act as surrogate egg donors and mothers.
Some scientists are suggesting this as a last measure to safeguard threatened animals that are difficult to breed in captivity. However, cloning is never going to be the panacea to the threat of extinction. The biggest problems faced by threatened animals are habitat loss, human encroachment on their territories, hunting and climate change. Cloning animals on the verge of extinction could helpspecies to hang on in zoos and parks, but it does little to generate the genetic diversity that is so important for the long-term survival of species. It also does nothing to address the root causes of extinction.
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