Overview
- A 20-year experiment reported in Nature Communications shows that recloned mice stopped surviving by the 58th generation using somatic cell nuclear transfer, which inserts an adult cell’s nucleus into an egg.
- Genome sequencing found more than 70 new DNA mutations per clone generation, about three times the rate seen in mice bred through natural mating.
- Late generations accumulated large structural damage to chromosomes, including cases where an entire X chromosome was lost.
- Warning signs emerged after about the 27th generation as fertility dropped, litters shrank, placentas grew larger, survival fell below 1% by generation 57, and none lived past birth at generation 58.
- Scientists disagree on the cause, with lead author Teruhiko Wakayama pointing to DNA harm from nuclear transfer and Shoukhrat Mitalipov arguing donor adult cells carry the extra mutations, a split that shapes next steps like stricter donor screening and possible gene editing and that raises caution for cloning in farming, conservation and de-extinction, as well as some medical uses.