History of animal testing
In 1996 Dolly the sheep was born, the first mammal to be cloned from an adult cell. The process by which Dolly the sheep was cloned utilized a process known as nuclear transfer applied by lead scientist Ian Wilmut. Although other scientists were not immediately able to replicate the experiment, Wilmut argued that the experiment was indeed repeatable, given a timeframe of over a year.
Hwang Woo-suk
In the late 1990s, the method that scientists used in cloning was somatic cell nuclear transfer, which is the same procedure that was used to create Dolly the sheep. This laboratory technique begins when an egg is taken from a donor and the nucleus is removed from the egg, creating an enucleated egg. A cell, which contains DNA, is then taken from the animal being cloned. The enucleated egg is then fused together with the nucleus of the cloning subject's cell using electricity. This creates an embryo, which is implanted into a surrogate mother through in vitro fertilization. If the procedure is successful, then the surrogate mother will give birth to a baby that is a clone of the cloning subject at the end of a normal gestation period. In 2014 researchers were reporting cloning success rates of seven to eight out of ten but in 1996 it took 277 attempts to create Dolly.