Japanese research shows that cloning cannot be performed indefinitely

A recent study in Japan shows that mammal cloning cannot be performed indefinitely. Harmful mutations accumulate in cloned animals over successive generations, eventually reaching a cloning limit. Researchers from the Radiation Effects Research Foundation and Yamanashi University published a paper in the latest issue of Nature Communications, stating that they conducted a continuous 20-year cloning experiment starting with a female donor mouse. They extracted somatic cells from the donor mouse and used nuclear transfer technology to produce the first-generation clone. About three months later, they extracted somatic cells from the adult cloned mouse for re-cloning. This process was repeated every 3 to 4 months, and the re-cloned mice were bred with normal male mice to study their reproductive ability. The research team reported that from 2005 to 2025, a total of 1,206 cloned mice were born. The success rate of re-cloning increased gradually from the first to the 26th generation. Starting from the 27th generation, the success rate declined, and the 58th generation clone mice died days after birth, marking the final generation. Analysis of the whole-genome sequences of the re-cloned mice revealed that, compared to naturally bred mice, cloned mice had a 3 to 4 times higher mutation rate. Additionally, harmful mutations that could affect survival increased with successive re-cloning. This indicates that there is a limit to re-cloning. (Xinhua)