Thursday, December 13, 2007

For the science boffins

Does DNA disappear?
I have been wondering this for some time. What happens to DNA? If one of my hairs or a fingernail fell on the ground, what happens to the DNA? Does it eventually just disintergrate or does it combine with the soil or something?
Yes!! I really need a holiday!!

10 comments:

Goose said...

Well, they've been able to extract DNA from dinosaur bones... not that it was good quality, but still... in a robust material like bone it hangs around!

mouthfulofpancake said...

Does it, in that sort of scenario, combine with other DNA? (sorry if this is simple science and I sound like I fell asleep in that particular class)

JollyRgr said...

I think that's actually a very good question.....I know that in my line of work it can hang around for quite a time but degrades....how far I'm not sure

Odyssey said...

Not good, great questions.

It will degrade, how rapidly depends on the conditions. Yes, it's been found in dinosaur bones. In that case it's survived because of the very special, and unfortunately very rare, conditions needed for fossils to form. The dead dinosaur had to be buried in mud and silt soon after dying, the silt had to dry out reasonably quickly and the resulting rock had to remain more or less undisturbed until found - that's why fossils are quite rare and there are gaps in the fossil record.

If the DNA is exposed to the environment it degrades much more rapidly, but it's very variable. It could last days, months, years or even decades. Eventually all DNA will degrade into smaller molecules that get absorbed into the surroundings. Ashes to ashes, dust to dust...

Would it combine with other DNA? No. Your DNA consists of two strands paired up with one another. Each strand consists of many millions of bases, of which there are four types (A, C, T, and G). The order in which those bases occur in your DNA determine all your genes - basically it's a blueprint for you. The bases pair, A with T and C with G. The second strand is complementary to the first - where the first has A's, the second will have T's etc. That allows the two strands to stick together in a very specific way. DNA from someone else, or another organism, won't have the same order of bases, and won't be able to pair as well, so your DNA stays your DNA.

Thus endeth today's molecular biology 101 lesson. Any questions? :-)

Goose said...

What he said...

Odyssey said...

Although he doesn't address the decay of DNA, you might want to check out Bill Bryson's A Short History of Nearly Everything." It's an easy and entertaining read that covers a hell of a lot of science. He's an author who's mostly famous for books that are highly amusing travelogues. The book he wrote about his travels in Australia is worth reading.

mouthfulofpancake said...

Thankyou

Odyssey said...

Bit much, wasn't it.

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