KELLY MCEVERS, HOST:
A few weeks ago on this show, we talked about what would have been Dolly the sheep's 20th birthday. Dolly was a scientific breakthrough, the first adult mammal to be successfully cloned. Then Dolly died early. Cloning continued, but under a cloud. That cloud is now lifting because Dolly's sisters have made it to a ripe old age, alive and healthy. NPR's Rae Ellen Bichell reports.
RAE ELLEN BICHELL, BYLINE: About four years ago, Kevin Sinclair inherited an army of clones. Very fluffy clones.
KEVIN SINCLAIR: Daisy, Debbie, Denise and Diana.
BICHELL: Sinclair is a developmental biologist at the University of Nottingham in England. The sheep he named are just four of 13 clones, but they're the most famous because of their relation to Dolly.
(SOUNDBITE OF SHEEP BLEATING)
BICHELL: The sheep that 20 years ago made headlines as the first successfully cloned mammal. Sinclair says think of them as sister clones.
SINCLAIR: They actually come from exactly the same batch of cells that Dolly came from.
BICHELL: Recently, Sinclair and his colleagues celebrated the sister clones' 9th birthday, which he says would be like celebrating the 70th birthday of a human. And in an article out today in the journal Nature Communications, Sinclair and his colleagues write that the clones' age, along with their strapping health, are encouraging. See, Dolly's life did not bode well for clones. She died young, at 6 and a half, with a nasty lung virus.
SINCLAIR: So that was really just bad luck and has nothing to do with the fact that Dolly was a clone.
BICHELL: But she also had bad arthritis in her knees and the tips of her chromosomes were short, both signs that she'd age more quickly than a normal sheep would.
SINCLAIR: That sort of threw fuel into the fire and strengthened the concerns that clones might be aging prematurely.
BICHELL: As the thinking went, because clones like Dolly were derived from the cell of an adult animal, her body might start out set to an older clock.
SINCLAIR: In other words, her biological age might be, you know, older than her chronological age.
BICHELL: It was a daunting concept for those in the cloning field, says Sinclair.
SINCLAIR: If you're going to create these animals, they should be normal in every respect. They should just be as healthy as any other animal that's conceived naturally. If that is not the case, then it raises serious ethical and welfare concerns about creating these animals in the first place.
BICHELL: But as he and his colleagues found, the 13 current clones indicate otherwise. The researchers measured the animals' blood pressure, metabolism, heart function, muscles and joints, looking for signs of premature aging. The results - normal, normal, normal.
SINCLAIR: If I put them in with a bunch of other sheep, you would never be able to identify them.
BICHELL: They had slight signs of arthritis, Debbie in particular, but not enough to cause problems. And it was expected at their age. The scientists haven't yet investigated the animals' chromosome tips but, says Beth Shapiro, the paper is already exciting enough.
BETH SHAPIRO: We're thinking about how we can use this type of technology to conserve populations that might be in danger of going extinct.
BICHELL: Shapiro is an evolutionary biologist at the University of California, Santa Cruz. She's interested in cloning endangered animals to keep them from dying off, and maybe even in resurrecting species that have already gone extinct.
SHAPIRO: This science is showing us in this paper is if we can get by what we know is the trickiest and least efficient part of this process then the clones that are born are, in essence, just like anything else that's alive - perfectly healthy and perfectly capable of living to old age.
BICHELL: As for the sheep clones, Sinclair says they'll continue to live normal sheep lives. Rae Ellen Bichell, NPR News.
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