Dolly the Cloned Sheep -- How Did They Do It?
The story of Dolly, the first ever mammal to be cloned from an adult cell, is incredible. Let’s figure out how these scientists achieved this feat.
The journey to Dolly's creation began with the exploration of somatic cell nuclear transfer (SCNT), which is the transferal the nucleus of a donor cell into an egg cell that has had its own nucleus removed. The goal was to see if an adult somatic cell, which had already differentiated into a specific cell type, could be reprogrammed to develop into a complete organism. Previous cloning efforts had been limited to embryonic cells, which have not differentiated into a specialized cell (like a red blood cell or neuron).
A team of scientists in Scotland chose a mammary gland cell from a six-year-old Finn Dorset sheep as the donor. This decision was inspired by the intention to demonstrate that even highly specialized adult cells could revert to a totipotent state and give rise to an entire organism. The donor cell's nucleus was carefully extracted and introduced into an egg cell from a Scottish Blackface ewe. This hybrid cell, containing the genetic material of the original Finn Dorset sheep, was hit with an electrical pulse to encourage cell division and development.
The resulting embryo was implanted into a surrogate mother, another Scottish Blackface ewe. On July 5, 1996, Dolly was born, a healthy lamb identical to her genetic donor (the original Finn Dorset sheep). The sheep was named after famous country singer Dolly Parton!
Dolly lived for only six and a half years (just above half of the usual lifespan for a Finn Dorset Sheep) but had a great impact in the scientific community. Her creation has led to developments in stem cell research, therapeutic cloning, and the study of genetic diseases.