'Dead End': Radical 20-Year Study Reveals Genetic Cloning Hits a Limit
"c0lo" writes:
After two decades of continuous work, researchers in Japan have discovered a genetic 'dead end' to mammal cloning.
The study began in 2005, when researchers, led by scientists at the University of Yamanashi in Japan, cloned a single female mouse.
They then re-cloned that clone by transferring its nuclear DNA into an egg 'emptied' of nuclear DNA, and so on and so forth, for 57 more generations, producing more than 1,200 mice from that single original donor.
Two decades later, the team was on their 58th generation, and the re-cloned mice had accumulated so many genetic mutations that they died the day after they were born.
The study is the first peer-reviewed research to 'serially' clone a mammal to this end.
"It has long been unclear whether mammals, unlike plants and some lower animals, could sustain their species through clonal reproduction alone," write the research team, led by geneticist Sayaka Wakayama.
"[O]ur results align closely with Muller's ratchet theory," they add. "This model predicts that in asexual lineages, deleterious mutations inevitably accumulate, ultimately producing mutational meltdown and extinction."
Since the first mammal was cloned in the mid-1990s, famously called Dolly the Sheep , scientists have learned a great deal about the whole process , and how to recreate an animal using very few cells.
Some conservationists hope that the practice can one day help us bring back species from the brink of extinction, and a few celebrities have even started cloning their pets .
While this might work for a while, over time, as clones are re-cloned and then re-cloned again, dangerous mutations can accumulate in the genome. How long this takes to kill a creature is unknown, and scientists in Japan wanted to find out using mice.
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