John Gurdon, Shoukhrat Mitalipov, Hans Adolf Edward Dreisch, Hans Spemann, etc. are people who contributed to the research and study of cloning. An example is when John Gurdon removed the nucleus of a fertilized egg cell and replaced it with a cell of a mature cell from a tadpoles intestine in 1962. The modified egg cell grew into a new frog showing that the mature cell still contained the genetic info needed to form all cell types. He contributed information needed for cloning.