91.   Because culling the stem cells destroys the embryo, however, the science has generated ethical questions.

92.   Because harvesting stem cells involves destroying an embryo, the research has prompted an ethical debate linked to cloning and abortion.

93.   Bush, as a candidate, opposed federal funding for research that destroys human embryos.

94.   Bush ultimately decided to allow funding for research using stem cell lines that were already in existence and where the embryo had already been destroyed.

95.   But federal law bans the use of tax dollars on any research that destroys embryos.

96.   But Bush was comforted by the number, Lefkowitz said, concluding that the multitude of cell lines would deter research labs from destroying additional embryos to secure more.

97.   But in order to extract stem cells, the embryo must be destroyed.

98.   But some oppose the research on the grounds that to get the cells, scientists must destroy human embryos -- fertilized eggs.

99.   But the federal government has not funded any research into embryonic stem cells because of a congressional ban on any research that destroys human embryos.

100.   But using embryonic stem cells is controversial, because embryos must be destroyed to harvest them.