In 1980 Frank Ruddle and his fellow scientists created the first transgenic organism. The animal was a mouse. The scientists used a very fine glass needle and injected a different DNA into a mouse egg. It contaminated the original DNA and changed its characteristics. Then the multiply injected embryos are inserted into a surrogate mother to develop the eggs. Only a few eggs that are changed with foreign DNA survive the injection.

http://www.answers.com/topic/transgenic-animal