Sunday, January 6, 2013
Science Sunday: telling time with DNA
I'm back! Time to talk a little about some science stuff :) I probably have a bit more fun with these posts that those who stop by my blog, but oh well. Today I thought I'd talk a little about something called the Molecular Clock--or how we use DNA and mutations to tell time.
What's been noticed is that mutations are always occurring in a really random fashion, but when you look at this randomness over a long enough time, a pattern starts to emerge. Basically, mutations (or differences in the A, T, C, & G's that make up a person's DNA in comparison with others) happen at a pretty regular rate. So while it's all still stochastic, we can say with a good amount of certainty that a new mutation will happen ever X years.
Okay, so if mutations happen at a pretty regular rate, all we need now is to know what the rate is. The way this can work (and there are several) is to look at two species or populations that we know exactly when they split apart. By comparing the differences that have happened since they split (assuming that they weren't there in the original, single population) with the known time, we have a rate!
This has been applied to a ton of other concepts (such as when people first arrived in the New World), and there is constant refinement of the rate of the clock going on, looking at things like generation length, areas of the genome that mutate more rapidly than others, etc. etc. While I personally think there are quite a few flaws and hurdles to using the molecular clock accurately, it is an interesting tool and provides some great corroborating evidence!