They're not top secret. Cloning involves the production of a genetic twin from a single cell, such as a skin cell, taken from an adult. In the simplest technique, scientists use an electrical shock to fuse a skin cell from the animal to be cloned to an egg cell whose genes have been removed. The combined cell starts to grow into an embryo that's genetically identical to the skin-cell donor, and that embryo is transferred to a surrogate mother's uterus to develop. Surprisingly, however, and important for those who wish to clone humans, the procedure appears to be quite safe for the surrogate mothers.
Most miscarriages go unnoticed because they occur so early in pregnancy.
Moreover, almost all clones that have survived to birth have been completely normal. Clones have grown up, mated and given birth to normal offspring. That all suggests that if a human clone were to survive fetal development it would probably go on to lead a physically normal life, scientists said. Psychological health might be another matter. Scientists and philosophers have questioned whether a child who is a genetic twin of his or her parent might suffer from an intergenerational identity crisis.