三毛猫はほぼすべてメスでオスはめったに生まれない/enのソースを表示

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{{豆知識
|番号=0042
|投稿者=まめち編集部
|本文=Calico cats are almost all female, and males are rarely born. Almost every male calico is an exception whose combination of sex chromosomes is unusual.
|なぜ=The gene that decides whether a cat's fur is orange or black sits on the X chromosome (identified in 2025 by a team including Kyushu University). A calico needs both orange and black, which means two X chromosomes, but a male is normally XY with only one X, so he comes out either orange or black.
|ジャンル=動物・植物
|ファクト度=A
|ファクト度の根拠=The mechanism and the breakdown of chromosomes were confirmed in primary sources (paper abstracts). Not S because there is no reliable source for how rare male calicos are (one in how many)
|ネタ度=S
|ネタ度の根拠=The colour of a familiar cat's coat depends on its sex, and the males are all exceptions
|便利度=該当なし
|便利度の根拠=A fact worth knowing for its own sake
|検証ステータス=根拠あり
|根拠1URL=https://pubmed.ncbi.nlm.nih.gov/40378840/
|根拠1要約=Abstract of the paper by Kyushu University and others (2025, Current Biology). A deletion of about 5.1 kb in the ARHGAP36 gene on the X chromosome is associated exclusively with orange coat colour
|根拠1格付け=一次
|根拠2URL=https://scienceportal.jst.go.jp/stories/20250623_g01/
|根拠2要約=Explainer by the Japan Science and Technology Agency (2025). A male is XY, so his single X chromosome makes him either orange or black. The male calico in the study had two X chromosomes (XXY)
|根拠2格付け=二次
|根拠3URL=https://pubmed.ncbi.nlm.nih.gov/10028567/
|根拠3要約=Abstract of a survey of UK vets (1999, Veterinary Record). Of 4,598 males, 20 were recorded as tortoiseshell or calico. Of the 11 whose chromosomes were examined, 6 were XX/XY chimeras, 2 were XXY, 2 were XX and 1 was XY
|根拠3格付け=一次
|根拠4URL=https://research.regionh.dk/en/publications/a-tortoiseshell-male-cat-chromosome-analysis-and-histologic-exami/
|根拠4要約=Danish case report (2013, Cytogenetic and Genome Research). An XXY male tortoiseshell cat had no germ cells in the testes: a classic sterile case
|根拠4格付け=一次
|根拠5URL=https://pubmed.ncbi.nlm.nih.gov/41818390/
|根拠5要約=Abstract of a Polish case report (2026, Sexual Development). An XX/XY chimeric male tortoiseshell Maine Coon mated and five kittens were born. Chimeric males can be fertile
|根拠5格付け=一次
|根拠6URL=https://www.nipr.ac.jp/science-museum/archive/special/ouchi/kikaku2020SPR/pdf/09.pdf
|根拠6要約=Exhibition material from the National Institute of Polar Research. Just before the first expedition sailed, a kitten was handed over with the words "a male calico brings good luck, take him as a charm for the voyage". He became Takeshi, the only cat to winter with the expedition
|根拠6格付け=一次
|根拠7URL=https://www.nipr.ac.jp/science-museum/archive/special/ouchi/kikaku2020SPR/pdf/02.pdf
|根拠7要約=Exhibition material from the National Institute of Polar Research. The first expedition's ship Soya left Harumi port on 8 November 1956
|根拠7格付け=一次
|根拠8URL=https://www.kumanichi.com/articles/1519091
|根拠8要約=Article in the Kumamoto Nichinichi Shimbun. Male calicos are "said to be one in 30,000"
|根拠8格付け=二次
|補足=Male calicos are born not only as XXY, with one extra X chromosome, but also as chimeras (XX/XY), where two fertilised eggs merged into one. In the UK survey, chimeras outnumbered XXY among the males whose chromosomes were examined. XXY males are normally sterile, but chimeric males have fathered kittens. Their rarity is often given as "one in 3,000" or "one in 30,000", but the original survey behind either figure was not found. In Japan they were prized as guardians of ships, and the first Japanese Antarctic Research Expedition, which sailed in 1956, took along a male calico named Takeshi, handed over as a charm for the voyage; he wintered at Syowa Station. Japanese Wikipedia's "Calico cat" (三毛猫) article also covers the mechanism and Takeshi.
|検証日時=2026-10-29
|検証方式=AI＋人
|本家既出チェック=本家に既出
|本家の該当ページ=https://ja.wikipedia.org/wiki/%E4%B8%89%E6%AF%9B%E7%8C%AB
}}