Sunday, November 05, 2006

 


科學論壇:複製人可能嗎?

以下是近幾年來關於複製動物的歷史:

1997年二月:在 276次的是在失敗後,由Drs. Keith Campbell 與 Ian Wilmut 所領導的研究團隊終於成功做出世界上第一隻複製動物....桃麗羊( Dolly),這複製創舉在當時引起全球熱烈地討論,由成熟體細胞複製出活體動物已不再是神話。(註桃麗羊1996出生於1997發表) 。

1997年六月:美國柯林頓(Clinton)總統基於人道與未知的考量,頒令禁止美國聯邦經費支助科學家進行複製人類的相關研究(為期五年)。

1997年七月: 製造桃麗羊的科學家們採用相同技術再做出保麗羊,惟這隻保麗羊帶有人類基因。

1998年二月: 韓國科學家宣稱成功複製出小牛(calf)。

1998年七月: 成功由體細胞複製出大約 50隻小鼠( mice),其中有些小鼠是經過多次複製(亦即由複製鼠的體細胞再行複製)。 技術上已經出現不同於複製桃麗羊所用的方法。

1998年十二月: 日本科學家成功複製出乳牛(cow).

1998年十二月:韓國科學家 Kim Seung Bo和 Lee Bo Yon「 宣稱」首度成功由人類婦女的卵子,經移除染色體並塞入同一婦女的體細胞後,培育出發展到「四細胞 」階段的人胚。這兩位科學家並強調他們的研究目的並不是想複製人類,而是希望在實驗室裡培育出可供人類病患使用的移植器官。基於人道的理由,複製的人胚已經被銷毀而實驗終止。(註)

2000年一月: 美國奧勒剛靈長類動物研究中心的科學家宣稱成功做出第一隻複製猴子Tetra,不同於複製桃麗羊的方式,該複製猴是透過將早期胚胎切割成四部份而獲得(故名Trtea)。這些科學家聲稱此實驗目的是希望製造出遺傳密碼完全相同的一對動物以進行相關實驗。

2000年三月: 第一隻複製豬成功發表,由當年複製桃麗羊的團隊執行,複製豬隻的目的在於提供與日俱增的人類器官移植需求。

2001年一月: 複製技術第一次成功用在挽救瀕臨絕種的保育類動物-白肢野牛( gaur:東南亞山區的一種野牛),雖然這頭牛在出生幾天後還是夭折,複製動物的技術提供保存稀有物種的一種途徑。
註:1998年韓國科學家複製人的實驗由於只提供照片(見左圖),缺乏可供學界驗證的基因證據,在當時引發許多質疑。以下是兩位科學家接受BBC專訪的新聞稿:The scientists who say they performed the experiment at the Kyung Hee Health Centre in Seoul, Dr Kim Seung Bo and Dr Lee Bo Yon, gave their first in-depth interview to BBC One's Panorama, broadcast on Monday. They said their experiment was for research purposes only but observers believe their aim is human cloning. Dr Kim said: "I believe the cloning of a human cell can provide a step forward in the treatment of human fertility."

"We don't have any material to judge. That's a big problem," said Dr Seo Chung Sun in Science magazine. The four cells claimed to have developed from an egg implanted with adult DNA were not preserved. Dr Kim Seung Bo explained why his experiment had been stopped after the cloned cell had divided to four cells: this was the stage at which cells would be implanted into a woman's womb and, for research reasons, he wanted to see if this stage could be achieved by cloning.
Professor Lee Silver, at Princeton University, USA, rejected this explanation. He believes the enormous outrage that followed the Korean scientists' announcement "forced them to backtrack and claim that it was only done for research. That makes absolutely no sense. Fertility clinics have one goal in mind - to help people have babies."

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