DOLLY THE LAMB, A MYSTERIOUS BIRTH ON A FARM
A NEW ERA FOR MANKIND?
Solomon Gobba, BSc Biomedical Science, Bachelors of Pharmacy IV, Makerere University
Dolly the sheep was the first mammal to be cloned from an adult somatic cell and was indeed a breakthrough in the field of biotechnology. The birth of dolly shocked the research community because although animals had been cloned before, creating a sheep from a single cell of a 6-year-old ewe was something many had thought impossible. Dolly was created using a process called somatic cell nuclear transfer, which involves taking the nucleus of a donor cell and transferring it into an egg cell whose nucleus has been removed.
Researchers had for many years been working on embryonic development starting with attempts in frogs that ably formed cloned tadpoles and even adult frogs by transferring the nuclei of embryonic or tadpole cells into frog eggs. These early attempts though successful met many obstacles as they were not able to use adult DNA. Whenever donor cells from an adult were used, no frog clone developed beyond the tadpole stage, this was primarily because only an egg cell possessed the ability of totipotency (Pennisi 1997).
Fertilization in vertebrates usually begins with the union of the sperm and the egg, with the sperm providing an activation stimulus that triggers the resumption and completion of cell division. In the unfertilized egg the cell-division cycle is stopped at a certain stage
Nuclear transfer disrupts fertilization by replacing the female genetic material of an unfertilized egg with the nucleus from a different cell(Gurdon and Colman 1999)
The process of creating Dolly began with the selection of a mammary gland cell from an adult sheep, a cell that had already differentiated into a specialized type of cell. The nucleus of this cell was then extracted and transferred into an egg cell from a different sheep breed. This egg cell had its nucleus removed, leaving behind only the cytoplasm and other cellular components necessary for development.
The egg cell was then stimulated to divide and develop into an embryo using electrical pulses, which triggered the cell to begin dividing and replicating its DNA. The embryo was then implanted into a surrogate mother sheep, where it developed into a lamb that was eventually named Dolly.
Dolly was born on July 5, 1996, at the Roslin Institute in Scotland. Her creation marked a significant milestone in the field of genetics, as it demonstrated that it was possible to clone a mammal from a single adult cell.
Several advances in the fields of agriculture, medicine, and biotechnology have been inspired by Dolly as scientists continue to explore the possibilities of cloning and genetic engineering. The success of dolly resulted in nuclear transfer experiment attempts in other species too with Dolly’s success inspiring new experiments looking at how DNA changes as a cell matures, what makes cells and organisms age, and how cell growth can go wrong, as in cancer (Pennisi 1997).
Dolly died at the age of six due to progressive lung disease. However, her legacy lives on, and her creation has paved the way for numerous scientific advancements that have the potential to improve human health and welfare in countless ways.
It has been many years since Dolly was created and it is still not possible to foretell exactly where cloning will lead (Wadman 2007). The success of Dolly and many more others over the years have shown what cloning can do for mankind. Could it one day have a place in giving infertile couples genetic offsprings? Could it be the solution to aging? Could it be the new edge for medical revolution? A lot still remains unknown and uncertain as regards genetic cloning with many ethical issues surrounding the topic, but one thing for sure is science always wins.
References
Gurdon, J. and A. Colman (1999). "The future of cloning." Nature 402(6763): 743-746.
Pennisi, E. (1997). Cloning: The lamb that roared, American Association for the Advancement of Science.
Wadman, M. (2007). "Cloning special: Dolly: a decade on." Nature 445(7130): 800.