Cloning is the process by which the nucleus of a specific type of mature cell is removed and fused with an egg whose nucleus has been removed. The result is an embryo that is genetically identical to the donor of the nucleus. Cloning has been successful in several species including sheep, mice, and cows. Tragically, human beings have been cloned and developed to an early embryonic stage in experiments. The purpose of human cloning to date has been for research and to develop an alternative to obtaining embryonic stem cells from surplus frozen embryos engendered at fertility clinics. If human embryonic stem cell research were successful, it would require the farming of human embryos through cloning. A new alarming development is that fetus farming through cloning may be necessary for embryonic stem cell research. Human cloning treats a human being as mere biological material, engendering human beings in order to destroy them.
The Gospel of Life (ns. 14, 57, 60–61, 63)
Catechism of the Catholic Church (ns. 2274–2275)
New Vatican document on bioethics (Instruction Dignitatis Personae on Certain Bioethics Questions)