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Cloned sheep shows signs of premature aging
Wonko42 writes "Everyone's favorite cloned sheep, Dolly, is showing signs of premature aging. Even though she's only three years old, her cells are acting like they're six years old. Scientists think this is because she was cloned using cells from an older sheep. "
Its been known for some time now that most cells don't live forever. I think it has actually been calcualted that human cells will only devide X numer of times before they stop working very well (where X is a number around 7x10^5 or so).
Some cells don't have this problem- noteably stem cells (the cells in your bone marrow from which all other cells come from) and cancerous cells. (!!!) I would have thought that Dolly would have been cloned from a stem cell. Maybe this was not possible when she was, uh, created.
The part of the article about telomeres is fairly accurate. Due to the way that DNA replicates, the ends of the chromosomes are not copied properly. There is an enzyme called telomerase that adresses this problem by capping the ends of the chromosome on each replication. (This also keeps the ends of the DNA from being degraded by enzymes in the cell's endoplasm). But telomerase doesn't do its job perfectly and the chromosome eventually starts to loose important parts of its DNA. How or even if this then triggers a self-destruct process in the cell is not really understood. Perhaps cloning can be used to study this.
2^5
The article points out that this may cause the sheep to die earlier than expected as all the cells are older. I would think that there would be other complications (or benefits) as well. As people age, their metabolism slows down. They also get wrinkly, smell funny, and go bald. Cloning of animals may finally help us to understand how aging works. Is it a result of time upon the body, or is it a result of genetics? We may even get some medical benefits as the body fights disease differently with age and we could start people off at an optimal age for immune system development (not being a doctor, this may well be birth).
:)
And if humans are ever cloned, what does this mean for things like Senior Citizen discounts and Social Security (I know this doesn't necessarily apply outside of the US). Is someone 65 years old because they've been on this planet for 65 years or because their cells say they're 65? Perhaps these old people who are climbing mountains and water skiing barefoot on one leg aren't really old, they've just been around for a while.