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Cloning Mammoths
Anonym Feigling writes "For your consideration... An article over at the New Zealand Herald discusses some of the challenges a japanes team faces as it attemps to develop a system to create a clone from 20,000 year-old mammoth tissue samples discovered in Siberia. It seems to me that shortly after death, any animal's/plant's "cellular repair mechanisms" (for the lack of a better...) will fail, and thus the probability of finding a single cell with perfectly intact DNA from which to create a clone is pretty well zero. Interesting stuff, but it seems that practical considerations (think code rot) would make it difficult."
Three considerations:
1) In order to PCR amplify something, you need primers which bind to the target areas and begin the replication. The primers need to have a known sequence, and we don't really know the mammoth genome, so we don't know what we're looking to amplify.
2) Mammoths have multiple chromosomes, so this isn't a one-step process. You'd need to repeatedly amplify section after section on each chromosome. Not impossible (per se), but not really feasible with todays technology due to:
3) Good day, high wind, Herculase (a PCR enzyme for long targets) can get 48,000 base pairs in one cycle with reasonable accuracy. The E. coli genome is 5.4 million base pairs. To PCR the entire E. coli genome you'd need to repeat the process 113 times to get the entire genome; if you're lucky enough to get the max every time, it'd take a lot of complex stitching to get it done. Of course, a mammoth is a lot bigger and more complex than a bacterium. The Fugu (pufferfish) genome is ~100 times bigger than E. coli (300 million), humans ~1000 times (3-4 billion). You can see the difficulty in using PCR for this type of application.
You are right, in principle, that you should be able to do all of these (eventually) but you also have to remember that each of these processes (not to mention troubleshooting!) takes materials (original DNA) in significant quantities. If we don't have a herd of mammoths, we probably don't have enough for what you suggest.