The numerous health problems that killed the most famous sheep in human history do not appear to have been caused by cloning. Dolly's four clones remain healthy, reaching almost old age.
The star of world science, 20 years ago, Dolly became the first successfully cloned mammal, but already at the age of five she was diagnosed with severe arthritis, and soon she moved with obvious difficulty. And at the age of six, the sheep died due to a rapidly developing pulmonary infection, having lived only about half the average age for its species.
This seriously scared the public, and even many scientists believed that Dolly's problems were created by the cloning process itself: errors that arise during this process will certainly lead to the appearance of prematurely aging individuals, as indicated by both arthritis and a tendency to severe course of a common retroviral infection. Other specialists pointed out that all diseases of Dolly are quite common in sheep and that it could simply be a matter of her initially poor health.
Debbie, Denise, Diana and Daisy, Dolly's clones obtained nine years ago, helped to put an end to this discussion. Of the 10 individuals bred then, most were born with serious disorders, but four turned out to be completely normal. Kevin Sinclair and his colleagues at the University of Nottingham reported on their health in an article published in the journal Nature Communications. According to scientists, animals feel great for their old age.
Year after year, Sinclair and his colleagues monitored the health and aging processes of 13 cloned sheep, including four clones derived from the same cells as Dolly. Blood pressure and insulin sensitivity, bone health and other parameters were compared with the same data for sheep of the same age, born naturally. According to scientists, over the years, only one cloned individual began to develop arthritis, but it remains in a moderate range, without requiring medical attention. Otherwise, they are perfectly healthy.
This is extremely interesting, because genetically Debbie, Denise, Diana and Daisy are completely identical copies of Dolly. Meanwhile, they do not experience any problems with arthritis and live a healthy old age. This contrast makes us think about the role that external conditions play in our life.