The concept of cloning living organisms dates back to ancient times. Any reproduction that does not involve the fusion of male and female germ cells can be classified as cloning. For instance, plants propagated by cuttings are clones. While plant cloning is relatively straightforward, animal cloning has presented more challenges. The most well-known example of a cloned animal is the sheep Dolly, born on July 5, 1996, at the Roslin Institute in Edinburgh, Scotland.
However, Dolly was not the first animal to be cloned. The initial breakthrough came in 1962 when Oxford scientists successfully cloned the American clawed frog. Later, in 1987, Soviet scientists cloned an albino mouse named Masha. Before Dolly, the Roslin Institute had already cloned two other sheep, Megan and Morag.
The Uniqueness of Dolly
Dolly stands out as the first warm-blooded animal that was 100% cloned using a revolutionary method. Unlike her predecessors, where nuclear material from germ cells was used, Dolly was created from a somatic cell—specifically, an udder cell from a six-year-old Finn Dorset ewe. The process involved transplanting the nuclear material from this somatic cell into an enucleated embryonic cell, which was then implanted into a surrogate mother. This method demonstrates the essence of cloning: taking a tissue sample from any part of a living organism and creating an exact genetic replica.
The story behind Dolly's name is equally fascinating. Since the cell used in her creation came from the udder, she was named after the singer Dolly Parton, renowned for her notable bust.
Dolly spent her entire life at the Roslin Institute, living for six years. She occasionally interacted with the media and gave birth to six lambs, fathered by a Welsh mountain ram named David.
Although sheep typically live for 12-14 years, Dolly was euthanised after developing lung tumours. This raised questions about whether cloning might contribute to disease development in cloned animals. However, there is currently no scientific consensus confirming this hypothesis.
"Zoo" of Cloned Animals
Following the birth of Dolly, cloning animals became a global endeavour, driven by scientific research and efforts to preserve endangered species.
In December 1998, Japan successfully cloned two cows, resulting in eight clones. The same year, the Netherlands produced two cloned calves named Holy and Belle.
In 2001, after 87 unsuccessful attempts, Texas scientists cloned a cat named Sisi (Copy Cat).
In 2005, Seoul University in South Korea cloned an Afghan hound using ear cell material. The process involved implanting ear cell nuclei into 1,095 eggs and transferring them to 123 dogs. Three dogs became pregnant, resulting in two puppies, of which only one survived.
In 2006, South Korean scientists cloned two members of an endangered wolf species. That same year, a ferret was cloned in the United States.
In 2009, Dubai's camel reproduction centre successfully cloned a camel named Injaz (achievement).
In January 2018, China achieved another milestone by cloning two cynomolgus macaques.
Horse Cloning
The first cloned horse, a Haflinger filly named Promethea, was born on May 28, 2003, at the Laboratory of Reproductive Technologies in Cremona, Italy. Creating Promethea required 328 attempts to produce a viable embryo.
On May 3, 2003, slightly before Promethea, the University of Idaho in the USA cloned a mule named Idaho Gem. Though not strictly a horse, as a mule, is a sterile hybrid of a donkey and a mare, Idaho Gem was significant in equine cloning. The project was funded by American Mule Racing Association President Don Jacklin. By 2006, Idaho Gem had competed in trial races, achieving notable placements, including two firsts, two seconds, a third, and a fourth in his first six races.
In July 2006, Idaho Gem competed in the Winnemucca, Nevada Mule Race, the first leg of the Triple Crown of Mule Racing, finishing third. This event marked a milestone in horse racing history as it featured the first clone to compete.
Pieraz, an Arabian horse born in 1983, was a two-time world champion in endurance equestrian sports over 160 km. Castrated at three years old, long before his championship, his rider Valerie Kanavi decided to preserve Pieraz's genotype. Genetic material was collected, and in 2005, his clone, Pieraz Cryozootech Stallion, was born. This effort was led by Eric Palmer of the French laboratory Cryozootech, which became part of the clone's name. Pieraz Cryozootech Stallion was later used for reproductive purposes.
Several laboratories worldwide now engage in horse cloning, including in the USA, France, Argentina, and China, leading to a growing number of clones. After the cloning of show jumping horses Pieraz and Kidam Revel, the International Equestrian Federation banned cloned horses from competition in 2007. However, this ban was lifted in 2012, allowing clones to compete internationally. Horse cloning has since entered a commercial phase, with clones used in breeding programs. The Belgian stud farm Zangersheide pioneered this area by allowing cloned horses to be entered into stud books.
Despite these advancements, stud books for thoroughbred and Arabian horses remain conservative, not registering clones or allowing them to participate in official races. However, since 2013, quarter horse clones have been registered in the US stud book and admitted to some Western competitions.
In 2023, China announced the successful cloning of Ursus, a racehorse imported from Germany. The clone, named Zhuang Zhuang (Growing Healthy and Strong), gives hope to Chinese horse breeders for solving horse shortages and achieving independence in equestrian sports.
Ethical Aspects of Animal Cloning
Animal cloning presents significant ethical challenges, primarily due to the high incidence of embryo death, often occurring at later stages of development. Many non-viable clones experience considerable suffering before dying, which, alongside religious objections, forms a central argument for bioethicists and opponents of animal cloning.
Despite the ethical concerns raised by animal rights activists, cloning endangered animals offers a crucial method for preserving species diversity on our planet. For instance, in 2009, scientists successfully cloned the extinct Iberian goat, though the clone did not survive long.
In 2020, the United States saw the cloning of a Przewalski's horse through the San Diego Zoo's cloning program. This endangered species, now preserved only in zoos, received new hope with the birth of a clone named Kurt.
Cloning also offers the potential to preserve and enhance the gene pool of horses, which is vital for maintaining and improving breed quality. Moreover, research in cloning aids in understanding and addressing genetic abnormalities in horses.
Research in animal cloning continues to evolve, with new findings emerging annually. As we advance technologically, the possibility of clone races may become a reality in the future, but only time will tell.