Japan has been cloning the same mouse continuously for 20 years. In the 58th generation, biology has said “enough”
When we talk about cloning living beings, many of us may think of the famous experiment. with Dolly the sheep. But he was not the only one, since in Japan a biologist has spent the last two decades taking life to its most extreme limit, since since 2005 his team has set itself a major challenge: serially cloning mice from a single original female donor. 20 years and more than 1,000 mice later, the experiment has collided with biology. A collapse. The results of this great cloning experiment were published recently in Nature and reveal the definitive collapse of the genetic line in generation number 58. A very important finding that not only demonstrates that the continued asexual reproduction of mammals is unsustainable, but also shows us why evolution opted so strongly for sexual reproduction and the constant renewal of DNA in our species. His story. The experiment by Japanese researcher Wakayama is a milestone in reproductive biology. In 2013, the team had already managed to clone up to 25 generations, as was then published in Cell Stem Cell; yesHowever, what seemed like a theoretically infinite process began to show serious cracks from generation 25-27. As the generations progressed, birth rates began to plummet, to the point where we are now, where he points out in his latest article that the incessant accumulation of genetic mutations was a constant. Here it was seen how the animals began to have serious genetic alterations with complete losses of chromosomes with a probability three times higher than natural sexual reproduction. Its consequences. That an animal sees its genetic material altered is not harmless, because these alterations were seen to directly affect embryonic development and the placenta, making each new generation more difficult to obtain than the previous one. But the critical point came in generation 58 of the mice, where the model finally collapsed. And the culprit of this collapse was none other than these genetic alterations, which curiously did not alter the physique of the individuals, who seemed completely healthy, but the weight of the genetic damage made it impossible to continue the chain. The impressions. From the Spanish countryside, Lluís Montoliu, CSIC researcher, has qualified this “heroic” experiment, since it suggests that this test would be impossible to do in Europe due to ethical standards and animal welfare that exist. But he sees it as important, since it proves the evolutionary superiority of sexual reproduction. The other side of the coin. Big questions arise here, since if serial cloning fails due to DNA fragmentation and damage… How is biology protected when it uses sexual reproduction? Here the answer is to have a constant renewal of the interior of our cells. Paradoxically, while science shows that copying the same DNA over and over again leads to genetic disaster, new clinical studies on human fertility are revealing that, to maintain the highest quality in male genetic material, frequent renewal is key. But in addition, it also makes it clear that we are still quite far from being able to clone humans to have two identical people, because in the end it is something that can go really wrong. Images | digitale.de In Xataka | A team of experts wants to resurrect extinct bison. There are many reasons to be skeptical
