Dolly, was the first mammal to be cloned by Wilmut et. al (1977). Dolly was the end result of a long research program founded by the British government at the Roslin Institute in Scotland. They used the technique of somatic cell nuclear transfer, where the cell nucleus from an adult udder cell is transferred into an unfertilized oocyte that has had its nucleus removed. The hybrid cell is then stimulated to divide by an electric shock, and the blastocyst that is eventually produced is implanted in a surrogate mother. Dolly was the first clone produced from a cell taken from an adult animal.
The following steps are involved in creation of Dolly :
Isolate donor nucleus : Isolate the nucleus from a somatic (non-reproductive) cell of a udder of adult donor sheep. The nucleus contains all the complete genetic material of the organism. A very small needle and syringe (suction device) is used to penetrate through the cell membrane to hold the nucleus and remove it from the cell.
Get unfertilized eggs: Retrieve some unfertilized egg cells (reproductive) from a female sheep. Many eggs are needed since not all of them will survive the various steps of cloning.
Remove the egg’s nucleus: Remove the egg cell’s nucleus, which contains only one-half of the sheep’s genetic material.
Insert donor nucleus : Insert the nucleus, with all its complete genetic material, isolated from the donor sheep mammal in Step 1 into the cytoplasm of egg cell that has no nuclear material. The egg’s genetic material now contains all traits from the donor adult. This egg is genetically identical to the donor adult cells.
Transfer the egg into womb : Transfer the egg into a receptive female sheep’s womb. Those eggs that survive and implant will continue to develop into embryos. When the offspring is born, it is a clone (genetically identical) of the donor sheep. After cloning was successfully demonstrated through the production of Dolly, many other large mammals have been cloned, including horses and bulls.
