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Goodbye, Dolly
goombah99 writes "Dolly, the famous cloned sheep has been put to death after being diagnosed with a progressive lung disease, according to many reports. This follows on earlier reports that she was prematurely aging, including developing arthritis. While one should be cautious about drawing conclusions from a single data point, its interesting to speculate." Here is a link to her birthplace courtesy of Captain Large Face
I believe that would be mutton. Lamb chops are less than 18 months old. Dolly's chops would be, uh, less than desirable at her age.
Public use of any portable music system is a virtually guaranteed indicator of sociopathic tendencies. -- Zoso
Although the shortening of her telomeres is well-publicized, it very well may have had nothing to do with the death. A somewhat more detailed story can be found here [Reuters].
The main suspected "kink" are the telomeres, and if we do discover it's a kink, it may be a difficult one to work around. Here's a good article on telomeres and telomerase.
Your telomere explanation was pretty good, except that telomeres aren't just any substance. They're DNA. The end of a chromosome has short repeating sequences of a few base pairs (ex: AATTAATT, etc.) which are not all replicated when a cell duplicates its genome and divides. This presumably acts as a molecular "clock" for the organism to keep track of its "age," but this is pretty controversial and unsubstantiated.
Click here to read more about telomeres. (Why don't more people link to Wiki?)
Even if this telomere function were well-established, it doesn't entirely explain the aging process. It seems that part of the process is due to oxidative damage caused by radical reactions in the mitochondria. But similar reactions happen in chloroplasts and some plants live for millenia!The exciting thing about biology is that you reach the frontiers of knowledge in the field during your first year of introductory undergraduate coursework. In math you reach the frontiers maybe by your fourth year or in grad school. For physics and chemistry, somewhere in between. Biology is full of unexplained phenomena. If you want to make a great fundamental discovery in one of the hard sciences, then become a biologist. So much is unknown!
Telomeres are repeating sequences of non-protein-coding DNA at the end of a chromosome. Due to an inefficiency involoved in the replication of chromosomes, they become shorter and shorter with each cell division. Eventually, the telomere is depleted and parts of actual genes begin to be cut off. This explains death by old age.
An interesting side note is that cancer cells do not undergo the shortening of telemeres unlike normal cells. As opposed to normal cells which have a finite lifetime, cancer cells are functionally immortal.
A little off topic, but still somewhat interesting.
It wasn't that Dolly was a clone. Dolly was kept indoors with a bunch of other sheep (some clones, some not) and this virus was spreading in the whole population. It doesn't sound like the disease was directly related to her being a clone.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
The telomeric shortening results in the 'Hayflic Limit' where mamalian cells in culture are observed to divide 50-80 times before killing themselfs, telomeric shortening is linked to this process, prehaps providing some sort of timer as to when to kill off the cell in order to prevent conditions such as cancer.
While the telomere exists as a protection against genetic instability arising from CRISIS, I think that ascribing it a role in 'aging' is a bit of a jump. I am much more comfortable with the idea that Telomeres act to help prevent genetic instability due to the problems associated with replication of linear chromasones. While the Telomere acts as a 'molecualr clock' of sorts, it is only really concerned with the cells DNA, aging in other ways (such as progressive modifications in collagen with increased age) is nothing to do with Teleomers.
As to the point on the aging process itself, i would argue that it is entirely independent of telomeric shortening, and that change in telomeric length is *just* a timer indicating the age of the cell/number of divisions to reach its current condition. The aging process is due to a large number of ancillary effects which have no relationship to the telomeres.
And yes, biology (or in this case, not to nitpick, genetics) is one of the places where you find yourself with the cutting edge stuff very early on. Makes for really interesting study, if a bit annoying that no text book you can buy is up to date enough.
Wrong for two reasons:
1. Genetic engineering is not "random". A better comparison would be a hacker taking 10MB of source code to some random program and adding an email client. (hey, like Emacs!)
2. The genetic code can handle quite a bit of "random" mutation. There are cases where it is extremely sensitive to mutation, such as sickle-cell leukemia (single poylmorphisim that causes hemoglobin to form chains), but there are "silent" mutations and even amino acid mutations that will have no effect.