Can a mouse be cloned indefinitely? Decades-long experiment has answers

https://www.nature.com/articles/d41586-026-00945-7

After 20 years, 58 generations and more than 30,000 cloning attempts, a team of researchers has hit the limit on the number of times a single mouse can be serially re-cloned.

The results, published on 24 March in Nature Communications1, suggest that asexual reproduction is ultimately unsustainable for mice, and potentially other mammals, too. The clones looked normal and lived as long as normal mice. But large mutations — including the loss of an entire chromosome — accumulated in the cloned lineage at an unusually high rate.

Those DNA changes could be the reason why subsequent cloning attempts failed, the authors argue. “That probably generalizes to any kind of vertebrate cloning, which has huge implications for agriculture,” says Michael Lynch, an evolutionary biologist at Arizona State University in Tempe, who was not involved in the study. “In any kind of animal breeding, once you have the optimal genome, the best way to keep it is by cloning — except for this mutation problem.”

Amassing mutations can be particularly perilous for populations that reproduce asexually, because there is no opportunity for their genomes to mix with those of another population. “Once the mutation is in the lineage, it’s there forever,” says Lynch. “There’s no way back.”
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