Overview
- Yamanashi University researchers, in a paper published Tuesday in Nature Communications, report that mouse re-clones stopped surviving at the 58th generation, with five pups dying within days.
- Starting in 2005, the team repeatedly cloned descendants from a single female’s somatic cells, with cloning success peaking at 15.5% by generation 26 and falling to 0.6% by generation 58.
- Genetic checks showed that from about generation 45, the re-cloned line carried three to four times more new mutations than mice bred by normal mating over comparable generations.
- Fertility plunged after generation 50 in the re-cloned line, with crosses to normal males restoring near-normal litters and pointing to mutation removal through sexual reproduction.
- The authors say the results limit long-term use of cloning for livestock improvement or saving endangered species, since cloning can preserve an individual animal but may not keep a healthy lineage without periodic breeding.