Human Cloning at Last

摘要

After more than a decade of failed attempts, it finally worked. This year, researchers announced that they had cloned human embryos and used them as a source of embryonic stem (ES) cells-a long-cherished goal. Able to develop into any tissue while providing a perfect genetic match to the cell that was cloned, the ES cells could prove a powerful tool for research and medicine. However, concerns about destroying embryos and the emergence of a cheaper, easier rival technique might keep human cloning for stem cells from becoming standard practice.