In John Gurdon’s 1956 nuclear-transfer experiment, a frog egg receiving a nucleus from a tadpole cell developed into a normal tadpole.
Gurdon removed the nucleus from an unfertilized frog egg and inserted a nucleus taken from an intestinal cell of a tadpole. Some reconstructed eggs developed through embryonic stages, proving that a differentiated cell nucleus still contained the genetic information needed to direct complete development.
The result challenged the idea that cell differentiation permanently removed genes. Instead, it suggested that mature cells usually keep the full genome while using only selected genes. Nuclear-transfer research later contributed to cloning, stem-cell biology, and cellular reprogramming.
Gurdon shared the 2012 Nobel Prize in Physiology or Medicine with Shinya Yamanaka for discoveries concerning mature cells and reprogramming them into pluripotent cells.