1995: A precursor to Dolly.
|In July 1995, Ian Wilmut and Keith
Campbell of the Roslin Institute in Scotland
successfully cloned two sheep, named
Megan and Morag, from differentiated embryo
cells. The idea to clone sheep was arrived at by Ian
Wilmut as an answer to a gene insertion
project he was researching. At the time, time inserting
genes into embryo cells was a
difficult and tedious process. Few embryos survived the
insertion of a gene, even fewer incorporated the gene
into their genetic code, and even fewer organisms
developed properly and used the gene in all of their cells. In 1986, when
Wilmut heard a rumor that Steen
Willadsen had successfully cloned cattle from
differentiated embryo cells, he decided to abandon
traditional gene insertion methods and investigate the
possibility of cloning. He knew that older cells could
more easily be manipulated in a lab. If cloning from more
advanced cells was possible, Wilmut knew he could
manipulate these differentiated cells in the lab, and
then produce a limitless number of clones from them. In
1990, Wilmut teamed up with cell cycle biologist Keith
Campbell to begin the cloning study.
Building upon earlier research by Lawrence Smith of the Roslin Institute, Campbell believed that in order for cloning by nuclear transfer to work, the two cells, the differentiated embryo cell and the egg, had to be synchronized in their cell cycles. As cells duplicate, they follow a certain pattern in checking and duplicating their DNA. It was believed that if the DNA of the embryo cell was not in the same stage of the cell cycle as the egg's cell DNA, then cloning would be ineffective. Campbell also believed that directly after fertilization, the egg enters a state of suspended animation, the Gap Zero, or G0 state, while it coordinates its two sets of DNA. In this case, the embryo cell should also be in the G0 state. To solve this problem, Campbell devised the clever process of starving the embryo cell until it entered the suspended state, G0.
After synchronizing the cell cycles, Wilmut and Campbell then proceeded to fuse the differentiated embryo cell with an enucleated egg using an electric current. From the process, Wilmut and Campbell obtained two live Welsh mountain sheep, Megan and Morag, which where cloned from differentiated embryo cells.
Copyright 1998 by team 24355 and Kayotic Development.