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Study Reveals Genetic Limits in Mouse Cloning After 58 Generations

3/30/2026

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Summary

Story summary

A 20-year study at the University of Yamanashi reveals genetic limits in mouse cloning.
They cloned a single female mouse for 58 generations.
Birth rates declined by generation 27.
The 58th generation was unviable.
Genome sequencing shows mutations accumulate and defects pass on without reshuffling, while later generations arise through sexual reproduction, partially restoring litter sizes.

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Story summary

A 20-year study at the University of Yamanashi reveals genetic limits in mouse cloning.
They cloned a single female mouse for 58 generations.
Birth rates declined by generation 27.
The 58th generation was unviable.
Genome sequencing shows mutations accumulate and defects pass on without reshuffling, while later generations arise through sexual reproduction, partially restoring litter sizes.