動物的品種不同,其特徵亦會有所不同。以狗為例的話,金毛尋羊犬以及臘腸狗就是非常鮮明的例證。491Please respect copyright.PENANAE3TTsaDRDI491Please respect copyright.PENANARjn6IT3E4Q
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至於牛隻,農場飼養用的大致分為兩種,主力出產牛奶的乳牛(Dairy Cattle)和主力屠宰成肉類出售的肉用牛(Beef Cattle)。491Please respect copyright.PENANA7uzhEVrevX
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各舉一例的話,前者品種例子為Holstein(荷斯坦),而後者則為較為廣泛認識的Angus(安格斯)。491Please respect copyright.PENANA3HzOis0jO1
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牛天生會否長角,將視乎品種而定。大多數的乳牛品種天生均長有角,而食用牛多數的品種則天生無角。491Please respect copyright.PENANAqebRBG59uz
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這裡讓農夫感到煩惱的是,乳牛隻會利用頭上的角互相攻擊對方甚至自己。491Please respect copyright.PENANAoV3Oou8ysv
因此慣常的做法會麻醉牛隻然後再進行除角手術,以免牛隻受傷因而損失獲利,但這做法引起動物權益成員的關注及爭議,認為此舉會對牛隻帶來創傷。491Please respect copyright.PENANA94fL7HoIRL
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(圖2)最為有效率及一勞永逸的解決辦法,自當然就是培育沒有長角的品種,一直傳遞下去。491Please respect copyright.PENANA9Cyje8uY9a
有科學家致力尋求發現,發現牛隻基因染色體1的某一段位置的重覆區域,將會導致乳牛品種不會長出牛角。491Please respect copyright.PENANAphZvRQtwuW491Please respect copyright.PENANAKbGptguUGd
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(圖3)因此,他們嘗試抽取長角品種的皮膚細胞,利用CRISPR基因編輯技術在那段基因區域上加添重覆區域(Ref1),再經過一系列的工序,將已編輯的細胞人工培植到牛隻身上,觀察誕下的胎兒會否長出牛角。491Please respect copyright.PENANAJ4YMV9hSJ3491Please respect copyright.PENANA7GDJYBEyvY
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(圖4)最終所誕下的牛隻的而且確沒有長角,但因器官衰竭等問題很快便與世長辭。491Please respect copyright.PENANAmH3NL56ca0491Please respect copyright.PENANAXjKFqdlDuZ
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這研究確實了CRISPR技術在牛隻的應用,但顯然仍有一系列的應用問題需要改善。在這實驗中,6隻人工培植受孕的牛隻中,只有一隻成功誕下嬰兒。491Please respect copyright.PENANADwp3FrXXc0
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至於為何不重點培育沒有長角品種的乳牛,原因是牠的產奶量較其他有角品種的最少。491Please respect copyright.PENANA3zrIHiHvvR
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農父及科學家的最終目標,當然就是希望培植沒有長角而產奶量豐盛的牛隻。但這做法是否符合動物權益,這又會是一場永無休止的辯論。491Please respect copyright.PENANAmGSlzoULto
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Ref1:https://www.nature.com/articles/s41598-020-70531-y491Please respect copyright.PENANAFVZQeP2NNN