In a pair of highly publicized articles, the South Korean scientist Hwang Woo-Suk claimed to have produced human embryos by cloning and to have generated from them several viable stem-cell lines. Hwang's work was heralded by supporters of embryonic-stem-cell research as a great step toward the goal of using embryonic stem cells to treat diseases and afflictions. What had them excited was Hwang's claim to have produced stem cells that match the DNA of the somatic cell's donor, thus defeating (or substantially diminishing) the number-one problem faced in transplant procedures, namely, the rejection by the body's immune system of genetically...