It is not yet known whether clones will develop and age normally, or whether subtle failures in genomic reprogramming or genetic imprinting might lead to various defects. Theoretically, tissues generated from cells cloned from a patient's own adult nucleus should not trigger an immune response, but it is possible that subtle differences caused by the foreign cytoplasm in the donor egg might cause a rejection response. Although scientists at Duke University suggested that human clones might not experience the problems encountered in cloned animals, the risks remains very high and quite unpredictable. Eventually animal research may indicate that human cloning can be accomplished with no greater risk than in vitro fertilization posed when Louise Brown, the first "test-tube baby" was born in 1978. However, scientists generally agree that human reproductive cloning should not be permitted before the scientific and technical issues have been clarified.
After a heated debate about human cloning in 2001, the U. S. House of Representatives voted 265-162 to institute a total federal ban on human cloning. The bill included penalties of up to 10 years in prison and a $1 million fine. The House rejected competing measures that would have banned cloning for reproductive purposes while allowing nonreproductive or therapeutic cloning for scientific research.
Non-reproductive cloning is legal in the United Kingdom. Since the early 1990s British scientists have been allowed to create human embryos for research purposes and perform experiments in therapeutic cloning. The Human Fertilization and Embryology Act of 1990 established a system for regulating the creation and use of embryos.
Research leading to reproductive cloning is banned, but therapeutic cloning in order to generate healthy replacements for diseased tissues and organs is permitted. Some ethicists and religious leaders object to all experiments on embryos, while others argue that even therapeutic cloning should be banned because it would eventually lead to reproductive cloning. While human cloning and human stem cell research are actually technically distinct, these issues have become virtually inseparable because both involve the use of human embryos.