http://www.cbc.ca/stories/2003/02/14/dolly_obit030214 Dolly the cloned sheep dies Last Updated Fri, 14 Feb 2003 18:03:50 LONDON - Dolly, the world's first mammal cloned from an adult, has been euthanized, scientists said Friday. A veterinary exam confirmed the six-year-old sheep had a progressive lung disease. Her cells had started to show signs of aging faster than a typical animal. Dolly, the world's most famous sheep, has died Researchers at the Roslin Institute in Edinburgh, Scotland, cloned Dolly, who was born in 1996. The birth was anounced on Feb. 23, 1997. Sheep normally live to age 11 or 12, according to Dr. Harry Griffin of the Roslin Institute. Post-mortem tests are being done, and the findings will be reported, he said in a statement Friday. He added lung infections are common in older sheep. Last year, Dolly's creators said the sheep had developed arthritis at a relatively early age, but was responding well to anti-inflammatory drugs. Apart from the arthritis in the hip and knee of her left hind leg, Dolly had been a healthy animal that gave birth to six lambs, the team's creator, Dr. Ian Wilmut, said in Jan. 2002. Scientists have found problems with cloned animals. Most attempts end in failure because the fetuses have oversized organs in the womb or are born stillborn. Other cloned animals have been born twice as large as normal. Last week, scientists in Australia announced their country's first cloned sheep had died unexpectedly. Post-mortem tests failed to identify a cause of death. Cloning experts say it is important to know whether Dolly's disease was related to cloning technology. The sheep deaths will likely add to the debate over whether using adult cells to clone animals inevitably causes errors in the copy. In December 2002, the Roslin Institute warned of the dangers of cloning a human. The Clonaid company announced the birth of the world's first human clone on Dec. 27, 2002. Scientists were skeptical of the claim, which hasn't been verified by independent tests. Written by CBC News Online staff
RIP Dolly... I would not be surprised to see signs of accelerated aging in cloned creatures. From my understanding of DNA - molecular biology specialists feel free to correct me or explain it more completely - a unique set of chromosomes with its own DNA blueprint is created every time the two haploid (sperm and egg) cells combine. Every time the chromosome goes through replication - if I understand right - it loses a little bit off the end of the DNA strand, called a telomere? These genes don't really code for anything but are thought to protect the rest of the strand against damage and mutagens. After enough cell divisions (--> old age), the end of the DNA strand is not as well protected and that may be why cancer rates, etc. increase sharply for people over 70. In other words - sorry, people, but our mortality may be written in our genes. With a cloned creature, the complete DNA blueprint is taken from another organism and has already undergone plenty of cell divisions before "Dolly" is even conceived. So it doesn't have as many left before the telomeres start getting eroded to the point where the DNA is vulnerable to those diseases that are caused by genetic mutation. Anyway, tricky stuff... not that I ever liked the idea in the first place, but there's a lot that has to be figured out before anyone should even think about cloning a human.
I believe stem cells and cancer cells have the ability to regenerate their telomeres. Whether or not research on that front will pan out is still in question since our understanding of aging is still in the infant stage.
Isabel, When you know as much about a subject as you do, you don't have to use question marks to see if anyone else knows better. Trust me, we are all ignorant to this process. Sounds interesting though. Don G
Whatever was the final resolution about those wackos who claimed to have cloned the first human baby? I remember there was much skepticism, but it all seems to have just faded into black.
So does having a long telomer string make a species long-lived? Do they know why giant tortoises can live for hundreds of years?
