The sheep code named 6LL3 – or more endearingly, “Dolly” – is perhaps the world’s most famous sheep. Born in 1996, Dolly is known not only as the world’s first cloned sheep, but the first mammal cloned using the nuclear transfer of an adult somatic cell.
Scientifically, cloning Dolly was a breakthrough, but the event had many social implications as well, casting the concept of cloning into the spotlight and causing quite a debate worldwide as to the ethics of the whole process.
In this guide, we’ll talk about both the process of cloning Dolly, why it was an amazing scientific feat whether you agree with it or not, and discuss some reasons why cloning Dolly became such a controversial matter. For a bigger focus on the way cloning Dolly worked biologically, check out this introduction to biology course.
Who was Dolly the Sheep?
Dolly was a female sheep cloned successfully from an adult Finnish Dorset sheep’s mammary gland cell and the enucleated egg of a Scottish ewe. Born on July 5th, 1996 at the Roslin Institute at the University of Edinburgh in Scotland, Dolly’s birth was the result of 277 attempted clonings by the research team at the Roslin Institute, which included embryologist Ian Wilmut and biologist Keith Campbell. Because she was cloned from the cell of a sheep’s mammary gland, she was named, perhaps in questionable taste, after Dolly Parton. If you don’t get the joke, you probably shouldn’t ask!
Despite being the first successfully cloned mammal, Dolly lived a rather healthy life, up until the end. She lived at the Roslin Institute, where she was born, and had six lambs of her own after being bred with a Welsh Mountain ram.
Dolly was euthanised on February 14th, 2003 at six years old, due to her debilitating arthritis and a lung disease. Neither of these illnesses were attributed to Dolly being a clone, despite her dying at a rather young age for a Finnish Dorset, which are expected to live for around 12 years.
There was one theory, however, that speculated Dolly was born with the same genetic age of the sheep she was cloned from: six years old. Researchers began speculating about this possibility when Dolly was just one year old, after a series of tests revealed something odd about her telomeres. Telomeres are DNA regions that exist at the end of chromosomes, and Dolly’s were much shorter than they should have been for a sheep of her age. This theory was never quite confirmed.
If you’re interested in learning more about the technology behind cloning, start your studies with this course on biology.
How Did Cloning Dolly Work?
You might benefit from this guide on biology vocabulary before getting into the technical aspect of cloning, but we’ll explain most of this on the way.
Dolly actually had three separate mothers, three sheep that each played a significant role in Dolly’s cloning and birth. One was a black-faced ewe, which provided the egg, the second was a white-faced sheep, which provided the mammary gland cell, and the last was a black-faced ewe, which acted as the surrogate mother in which the embryo was implanted. With the help of these three sheep, cloning Dolly was made possible, but not without the bizarre process of somatic cell nuclear transfer making it all happen.
What scientists did was take an unfertilized oocyte, or an egg cell, from one sheep, remove the nucleus, and replace it with the nucleus of an adult cell from another sheep. A nucleus is a protoplasmic mass that exists in eukaryotic cells, directing much of the cell’s metabolic functions and other important processes, as well as housing a complete set of genetic material for that cell. Adult cells have disabled, so to speak, the genetic information that they don’t need. (Check out this course on organic chemistry if this is of interest to you!)
This is where using the nucleus of an adult cell became complicated. The process of resetting the adult nucleus to an embryonic state is difficult, which is why Dolly only came around after a whopping 277 attempts. The cell and the enucleated egg from which Dolly would be cloned were fused together using electricity. This also promoted cell division. Then, scientists implanted the egg into the uterus of what would become Dolly’s surrogate mother.
When Dolly came out genetically identical to the white-faced sheep from which the mammary gland cell was taken, and not the black-faced ewe the egg was donated by, or the black-faced ewe that carried Dolly to term, scientists knew they had successfully cloned a sheep using the process of nuclear transfer. Check out this
Why was cloning Dolly controversial?
After Dolly was successfully cloned, several animals – from pigs to bulls to horses – were cloned in the years to come. While the science of cloning had been in existence for decades, and Dolly’s cloning meant something huge for the community, this was all happening under the harsh scrutiny of the public eye – something that had not really been the case before Dolly.
Cloning Dolly put cloning into the spotlight of the mainstream media, and people around the world began to raise all sorts of ethical questions. For instance: just because we can clone animals, does this mean we should? What does the reality of an artificially manufactured, living thing mean in regards to religion? Is Man playing God by cloning animals? What would it mean to clone a human? Does a living thing lose something inherent to its being in the process of cloning? That’s getting pretty heavy, but when it comes to debating the ethics of cloning, this was and still is some heavy stuff.
You can debate the ethics of cloning for as long as you want, but there’s no doubt that the technology of cloning was a major scientific breakthrough, no matter how you think the technology should be used (or not used). Learn more about related concepts in this course on biomedical engineering. Or, debate your friends with this guide on the pros and cons of cloning.