Fertility doctors would implant an embryo in a womb within days of creating it. Cell scientists, however, would extract the stem cells from the embryo at that point and grow those cells in a lab to make tissues. The extracted cells could never become a baby. Religious and pro-life groups, though, argue cloning for any experimentation breaks the sanctity of human life and should never be accepted. But removal of these cells kills the human beings from which they are taken.
Therapeutic cloning means killing.
Charities such as Life would like to see more work done to follow up research showing that adult stem cells, instead of embryonic ones, could be used to develop tissues and organs. In 1997 Dolly the sheep became the world's first mammal cloned from an adult cell. It was part of a project to try to make human recipients less likely to reject pig organs after a transplant operation. Researchers try to alter pig genes and then clone the modified pigs as a source of organs. Some pig parts like valves are currently used in areas like heart transplants.