Time：2023-03-27 10:35:27 source：ucutxmastrees.com author：Fish Read：381次

A world first! China clones arctic wolves, will cloned animals really age prematurely? Can they reproduce?

On September 19, Beijing Wildlife Park released an ordinary and special video: a video of a lively little wolf rolling on the ground and gnawing at bones. The video itself is very ordinary, but the identity of this little wolf is not ordinary. It is the world's first cloned Arctic wolf, and a second cloned Arctic wolf will soon be born. The news of the cloned wolves gave us too many questions, especially when it comes to this particular technology of cloning. Why clone an arctic wolf? Will cloned arctic wolves age as prematurely as cloned Dolly the sheep? Is it capable of reproduction? Can these long-extinct animals be "revived" through this technology?

Why cloning arctic wolves?

Arctic wolf, also known as white wolf, is a subspecies of gray wolf, about 70 cm in height and 80 kg in weight. They originated 300,000 years ago and lived under the same sky as mammoths, saber-toothed tigers, cave lions and other animals, but the Arctic wolves survived the extremely cold ice age and became one of the few polar regions in the desolate Arctic. It is also known as the "Three Arctic Hegemons" together with polar bears and arctic foxes. Even in the arctic temperature of minus 40 degrees Celsius all year round, arctic wolves can still sleep in the open air, endure starvation for weeks, walk more than ten kilometers at 10 kilometers per hour, and chase their prey at 65 kilometers per hour. Has great vitality, endurance and adaptability. But their survival situation is not optimistic. Because of the scarcity of food in the Arctic, they have a strict reproductive system. Usually, only the leader of the wolf pack and his wife have the right to mate. Unless the wolf population is greatly reduced, other wolves will not have the freedom to reproduce. A wolf pack may have only one litter of cubs a year, which is raised by the entire pack. This special reproduction method is doomed that the number of Arctic wolves will not be too many. Then there are the clichés of habitat destruction and rampant poaching, with at least 200 Arctic wolves killed each year. In this case, the Arctic wolf is on the brink of extinction and is placed on the Red List of Threatened Species. There is no reproductive isolation between wolves and dogs. In the cloning technology, both oocytes and surrogates can be provided by dogs. Just like the cloned wolf mentioned above, its surrogate mother is a beagle. This makes cloning the Arctic wolf a lot less difficult. If it is not only an endangered species but also has reproductive isolation from other animals, it may be better to directly help them reproduce.

Do cloned Arctic wolves age prematurely? Is it reproductive capacity?

July 5, 1996, which is destined to be a day in history, the world's first cloned sheep Dolly was born. Its birth is considered as a major achievement of cloning technology in the scientific community. But unfortunately, when Dolly was 6 years old, she was suddenly pronounced dead, with half the lifespan of a normal sheep. Cloning Dolly the sheep has poured cold water on people's heads. Many people use Dolly's short life as evidence and claim that cloning technology will lead to premature aging and various diseases. Cloning technology is not as good as imagined. This argument is still today. There are still people who believe it. Is this true? Time goes back to 1999, when the birth of the cloned sheep Dolly set off a cloning frenzy in the scientific world, and it was in this year that the famous biologist Yang Xiangzhong obtained cells from a 13-year-old cow and successfully cloned a A calf named "Daisy". A 13-year-old cow, which is already in the 80s of a human, has long lost its fertility. According to the statement that "the age of the cloned animal is calculated according to the age of the cell donor animal", then "Daisy" was born at the age of 13 and should not have reproductive capacity. But "Dai Xi" is very healthy, and in 2001, "Dai Xi" also successfully gave birth to a healthy calf of 40.5 kg through natural breeding, so that this statement is self-defeating. This result proves that the cloned animals can still develop normally, become pregnant, and give birth to offspring, and it shows that the aged cells have been physiologically transformed into brand-new newborn cells after being cloned. A cloned animal is not a copy of the parent, but an entirely new individual. Then, a new study by German scientists also proved that during the cloning process, when the embryo reaches a certain stage of development, the telomerase in the cell will repair the telomeres to normal length. Some people may not know what telomeres are. To use a simple analogy, it is like a special clock. Every time it goes, the cell divides once. When the telomere, the clock of life, comes to an end, the cell no longer has the ability to divide. Ability, it will come to the end of the animal's lifespan. The telomere length is repaired during the cloning process, which means that the lifespan of the cloned animal is normal. The death of Dolly the cloned sheep may be due to the imperfect cloning technology at that time or just the death of a common disease. Because she actually has a group of cloned "sisters", in 2007, a researcher who participated in the cloning of Dolly used the preserved tissue to clone four more sheep, and they normally lived to be close to 10 years old. , which is about 70 years old in humans, and in good health. It seems that cloning does not necessarily lead to premature aging of animals, and cloned animals can reproduce normally.

Can cloning 'revive' extinct animals?

In 2020, American scientists cloned a new black-footed ferret using the frozen cells of a long-dead ferret. Endemic to North America, the ferret was once thought to be extinct, but in 1981 a farmer discovered a small herd of ferrets on his farm. Black-footed ferrets These black-footed ferrets were captured by people and tried to breed them artificially, but only 7 successfully gave birth to offspring, so today's black-footed ferrets are all close relatives, and scientists have "resurrected" them through cloning. This ferret is one of the wild ferrets that left no offspring, and her presence may enrich the ferret's genetic diversity. However, the reason why the black-footed ferret can be "resurrected" is because its remains have been properly preserved. However, in nature, many ancient creatures are left with only fossils after experiencing wind and rain and geological changes. The most important thing for cloning technology is to have complete DNA. It is undoubtedly difficult to extract complete DNA from these fossils. Heavy work. At present, the most promising ancient creatures are mammoths. There are many relatively intact individuals of mammoths preserved in the permafrost of Siberia. The environment of permafrost is very suitable for preserving mammoth DNA, but even if it can be extracted We cannot determine whether these DNAs contain other DNA contaminations such as bacteria and fungi. Mammoths and assuming that scientists can cultivate mammoth embryos, they can't find a suitable mother. Even today's Asian elephants, which are the closest relatives of mammoths, are much smaller than mammoths. Can the embryos be successfully transferred? , it is unknown whether the mammoth can be successfully delivered. Therefore, it is not impossible to "resurrect" those ancient creatures through cloning, but it is very difficult and the probability is very small. Not so long ago, creatures that have gone extinct in the past 100 years, such as thylacines, have a higher chance of being cloned successfully, but if the cloned individual genes all come from a single donor, then it is difficult for them to reproduce normally. . The thylacine cloning technology is still more valuable for those endangered, but not completely extinct animals, just like the black-footed ferrets mentioned earlier, to increase the genetic diversity of these animals. Rather than thinking about "resurrection" of ancient creatures, it is better to protect the existing endangered animals down-to-earth. References "Clone Animals Don't Mean Premature Aging" Chinese Academy of Sciences "Clone Cattle Breeds Naturally" Ding Baozhong "Arctic Wolf - White Spirit in the Polar Regions" Hai Cong "Can Extinct Animals Resurrection" Wang Xiaobing "Cloning Technology Brings "Resurrection" of Extinct Animals 》 Jiang Li

(责任编辑：Bird)

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