Not a Surprise

Scientists have repeatedly cloned a mouse.  Somewhere around generation 30, reproductive success dropped, and by generation 58, all of the mice were born dead.

This is not particularly surprising.

Sexual reproduction evolved as a genetic repair device, some bacteria exchange genetic material to this day.

Cloning does not necessarily cause genetic damage, but it necessarily fails to repair damage as sexual reproduction does. 

Here’s the cautionary tale you didn’t know you needed: cloning the same mouse in perpetuity will produce horrific affronts to mammalian biology.

A team of researchers in Japan discovered this firsthand. In a stunning experiment lasting two decades, they cloned a female mouse, and then cloned its clones, for 58 successive generations. But over 1,200 clones later, the experiment stopped, because by that last generation the mice kept dying immediately after being born, despite displaying no outward physical abnormalities.

The findings, published in a new study in the journal Nature Communications, suggest there’s a hard limit to duplicating mammals. And to scientists hoping for “infinite” cloning, this came as a major let down.

“We had believed that we could create an infinite number of clones. That is why these results are so disappointing,” study senior author Teruhiko Wakayama, of the University of Yamanashi, told Reuters.  

………

Perfect clones, it turns out, aren’t perfect clones. Sequencing their DNA throughout the generations revealed that they were accruing small mutations over time that snowballed into larger ones, even though the clones were superficially identical. In some cases, the clones even lost an entire copy of their X chromosome.

“It was once believed that clones were identical to the original, but it has become clear through this study that mutations occur at a rate three times higher than in ​offspring born through natural mating,” Wakayama said.