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Scientists harvested eggs from 25th-generation cloned mice and fertilized the eggs, which grew into these early-stage embryos. Credit: Univ. Yamanashi<\/p>\n
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.<\/p>\n
The results, published on 24 March in Nature Communications1<\/a>, suggest that asexual reproduction<\/a> is ultimately unsustainable for mice, and potentially other mammals, too. The clones looked normal and lived as long as normal mice. But large mutations \u2014 including the loss of an entire chromosome<\/a> \u2014 accumulated in the cloned lineage at an unusually high rate.<\/p>\n How Dolly the sheep\u2019s legacy lives on: CRISPR cattle and cloned camels<\/p>\n <\/a><\/p>\n Those DNA changes could be the reason why subsequent cloning attempts failed, the authors argue. \u201cThat probably generalizes to any kind of vertebrate cloning, which has huge implications for agriculture,\u201d says Michael Lynch, an evolutionary biologist at Arizona State University in Tempe, who was not involved in the study. \u201cIn any kind of animal breeding, once you have the optimal genome, the best way to keep it is by cloning \u2014 except for this mutation problem.\u201d<\/p>\n Amassing mutations can be particularly perilous for populations that reproduce asexually<\/a>, because there is no opportunity for their genomes to mix with those of another population. \u201cOnce the mutation is in the lineage, it\u2019s there forever,\u201d says Lynch. \u201cThere\u2019s no way back.\u201d<\/p>\n Instant gametes<\/p>\n In 1997, Teruhiko Wakayama, a reproductive biologist now at the University of Yamanashi in Kofu, Japan, and his colleagues were the first to make a cloned mouse<\/a> \u2014 a mouse that was an exact genetic copy of a single \u2018parent\u2019\u2014 using a non-reproductive cell from an adult animal. To do so, the scientists replaced the nucleus of a one-celled embryo with a nucleus taken from the non-reproductive or \u2018somatic\u2019 cell2<\/a>.<\/p>\n Since then, Wakayama has continued to push the boundaries of mouse cloning. He has used nuclei taken from live mice, dead mice, dead mice that had been frozen for 16 years, freeze-dried cells and cells in mouse urine3<\/a>,4<\/a>. He is currently trying to clone mice from cells found in mouse faeces. He and his colleagues have also successfully used freeze-dried sperm to fertilize mouse embryos \u2014 \u201clike instant coffee\u201d his website says \u2014 that orbited Earth for nearly six years on the International Space Station5<\/a>.<\/p>\n How quickly do humans mutate? Four generations help answer the question<\/p>\n <\/a><\/p>\n \u201cAll the themes in my laboratory are related to the goal of permanently preserving the genetic resources of all animals,\u201d says Wakayama.<\/p>\n Decades ago, he and Sayaka Wakayama, who is also a reproductive biologist at the University of Yamanashi and is married to Teruhiko Wakayama, embarked on an experiment to see how long a mouse could be preserved through cloning alone. In 2013, they reported that they had created a lineage stretching 25 generations6<\/a>. \u201cIt may be possible to reclone animals indefinitely,\u201d wrote Wakayama and his colleagues in their Cell Stem Cell paper.<\/p>\n","protected":false},"excerpt":{"rendered":"Scientists harvested eggs from 25th-generation cloned mice and fertilized the eggs, which grew into these early-stage embryos. Credit:…\n","protected":false},"author":2,"featured_media":402199,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[77],"tags":[3545,16970,18,458,1099,19,17,1100,133],"class_list":["post-402198","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-biological-techniques","tag-developmental-biology","tag-eire","tag-genetics","tag-humanities-and-social-sciences","tag-ie","tag-ireland","tag-multidisciplinary","tag-science"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/116286877394670493","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/402198","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=402198"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/402198\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/402199"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=402198"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=402198"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=402198"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/03\/d41586-026-00945-7_52202308.jpg\"\/)
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