Illustration of Cloning

Reproductive Cloning. To clone an animal, researchers first take mature cells, such as skin cells, from the animal to be cloned. Next, they take an unfertilized egg from an adult female of the same species and remove the nucleus, which is the cell structure that houses the chromosomes that contain an organism’s DNA. Researchers then place one of the skin cells next to the nucleus-free egg and apply an electric pulse, which causes the skin cell to fuse with the egg. The fused cell, which contains the skin cell’s nucleus, divides and forms an early-stage embryo. This embryo is implanted in the uterus of another female animal, called a surrogate mother, and allowed to develop. The surrogate mother then gives birth to an animal that is genetically identical to the adult that donated the skin cells. This newborn animal is referred to as a clone.