A clone can be defined as an offspring obtained from a single individual without fertilization. 

The cloned sheep Dolly was born as a result of a project led by Ian Wilmut and Keith Campbell from the Roslin Institute. Dolly was cloned in 1996 from a mammary gland cell of a Finn Dorset sheep, which was fused with an enucleated egg cell from a Scottish Blackface sheep. Dolly, who developed in the womb of another Scottish Blackface sheep, was a genetic copy of the Finn Dorset sheep.

During natural mating, as we know, only one sperm out of millions fertilizes the egg. Wilmut and Campbell realized they needed an alternative to sperm to create a new life. 

They used an electric shock method to facilitate the fusion process. This shock temporarily created holes in the membranes of the egg and mammary cell, allowing calcium to enter the egg and start a chain reaction leading to the development of a viable embryo. The cells began to divide and increase in number. A surrogate mother, prepared for pregnancy with hormones, was used to provide an environment where the transferred embryo could implant and develop. Dolly was born five months later.

Contrary to popular belief, Dolly was not the first cloned animal. Two earlier cloned sheep, Megan and Morag, created by Campbell’s efforts, did not attract much attention. However, Dolly’s case was different. Despite Dolly being born on July 5, 1996, her birth was kept secret from the media for a long time. When the news leaked in February 1997, it became one of the most discussed and celebrated events worldwide.

The scientific community was particularly intrigued because Dolly was produced from a body cell of an adult sheep. Until then, cloning efforts had used cells from embryos. Creating a living organism from a fully differentiated body cell was a significant scientific breakthrough. Before this discovery, it was believed that all cells in the body could be derived from embryonic cells and that this capability was lost after cellular differentiation. Wilmut and Campbell’s work disproved this view.

The cloning process was not as easy as it sounded. Wilmut and his team had to repeat the procedure 277 times before successfully creating Dolly. Even after transferring the clones to 13 different surrogate sheep, only one became pregnant, resulting in Dolly’s birth.

Dolly shared the same pen with Megan and Morag, but unlike natural sheep, the pen was not just a place to stay; it was their permanent home. Dolly was fed a special diet and received careful attention. She lived longer than most sheep, as they are typically sent to slaughterhouses at nine months old. Although Dolly was initially thought to be sterile, she gave birth to a lamb naturally in 1998, disproving this belief. Dolly later became pregnant again and had a total of six lambs throughout her life.
In February 2003, Dolly fell ill with pulmonary adenomatosis, a lung disease caused by a virus. On February 14, 2003, Dolly passed away.

This blog post has been verified by Doctor of Veterinary Medicine Yunus Emre AŞICI.

SOURCES

E. Ağacı, et al. Kopya Koyun Dolly Nasıl Klonlandı?. (10 Haziran 2015). Alındığı Tarih: 21 Aralık 2023. Alındığı Yer: https://evrimagaci.org/s/3673

Niemchick, Andrew ve Rogers, Kara. “İnsan Vücudu Sistemleri”. Britannica Ansiklopedisi, 29 Kasım 2023,https://www.britannica.com/topic/human-body-systems-2237111. Erişim tarihi: 21 Aralık 2023.