Ancient DNA

PyroX_Pro writes "An interesting read over at the BBC says that 400,000 year old DNA has been found. The DNA has been broken into tiny pieces, so there is little chance of bringing any of the species back from the dead. "Soil frozen into the ice has also yielded fragments of DNA of large prehistoric animals, including the woolly mammoth, reindeer and musk ox" "Cloning is in our view impossible at this stage. You'd need the whole DNA and you would have to constuct a primitive cell to put the DNA in," added Mr Gilbert. " Sure he says that now, but they may find a way to splice it with other DNA, and then, well you all saw the movies..."

Comments

Re:Gene sequencing/splicing

[!splut]

Excellent point; I was going to say something to that effect myself. Modern DNA sequencing techniques involve digesting or shredding massive genomic pieces of DNA into small fragments, in the neighborhood of 300 - 700 base pairs in length. The reason for this lies with the sequencers, which can only get a maximum of around 700 base pairs of reliable data per run.

Sequences of the resulting fragments of DNA are used to reconstruct the entire genome based on the overlap between sequenced fragments. Overlap and a certain degree of redundency, in fact, is necessary as a form of error checking, as sequencing methods have an inherant error rate.

So, if these prehistoric DNA fragments overlap sufficiently, it is theoretically possible for their sequences to be used to reconstruct an entire genome.

However, a bigger concern might be damage to DNA. DNA, like all biological molecules, suffers a certain degree of degredation over time due to high energy radiation, exposure to free radicals, normal biochemical processes (such as nucleases present in the original cell, or secreted by microbes in the environment), etc. There are biochemical mechanisms in living cells that continually work to repair these damages, but in a dead, frozen cell those systems would not be present, and the DNA would just accumulate damage. Such damage can inhibit or introduce large error into sequencing attempts, so it is possible that the original sequence of the DNA can never be recovered.

Re:Gene sequencing/splicing

[nobody69]

I thought the way the Human Genome project worked was by breaking our DNA into lots of small bits and sequencing them in parallel, then putting those sequences together in a computer.

When scientists do sequencing on DNA, they use enzymes that cut the strands at specific sequences (frex: an enzyme will 'look' for the sequence ATGCCGTAATCGA and cut the strand so you get a segment that ends ATGCCGTA and one that begins ATCGA) so you you get known beginning and ending points. Also since the DNA strands are complementary you know that if one side of the double helix has the ATGCCGTAATCGA sequence, you also know that the other has TACGGCATTAGCT. Which helps with making sure that you are connecting your cut strands in the right order. If your strands are broken into too many small pieces in a random pattern it's much harder to put them back together again. It's the difference between re-assembling an Encyclopedia Brittanica that has been cut between each article and one that has been run through a cross-cut shredder.

The one thing Jurassic Park never explained was how they made the dinosaur eggs.

They called the FX department. ;)