Do DNA mutations put us in danger?

CRobin23 asks this question on the forum. Geneticist Hannah Thompson has an answer...

Hannah - Yeah, that's a great question. That's exactly how certain diseases happen, just like cancer. So if we take a step back and we look at our genome, we have 2.9 billion base pairs in it, which is about 725 megabytes of data, which is actually the same as a typical film.

Chris - They're the genetic letters, those base pairs.

Hannah - Yes, that's right. So about one out of every hundred thousand times you sort of, try and copy those base pairs. You get a mistake, and that's actually completely normal in itself and the cell is really, really good at figuring out what's happened.

Chris - And that would happen, for instance, when cells are dividing, they've got to copy the genetic information to put a copy into the new cells they're making, and that's when those errors might creep up.

Hannah - Yep, that's right. Luckily for us, only 1% ish of our genome is sort of really interesting, and well what we know of so far is really useful for us to be alive. And so the mutations in that part of the gene region obviously are still common, but the cells are really, really good at detecting them and stopping them from happening. And obviously you can personally do things that stop them from happening a bit more. So less UV, less smoking, less red meat, that kind of stuff. And different kinds of cells have different kinds of mutation rates. So there's a really cool study by Peter Campbell on eyelids. So in middle aged and elderly people, they have about 60 to 180 mutations in each cell on your eyelid, which is pretty mind blowing.

Chris - Is that because it's been exposed to the sun a lot.

Hannah - Yeah, exactly that. But that doesn't necessarily mean that you will get cancer. Some of those mutations might not be in the really important genes.

Chris - Is it not important also, to point out that actually, this is how evolution happens and the way in which we adapt to the environment we live in is because we do hand on genetic spelling errors to our offspring, and the consequence of that is that sometimes it might be bad for them, but sometimes it might be good.

Hannah - Yeah, it's important to have all really useful ones, that's for sure. Yeah, but we know that the mutation rate of the sperm cell for example, is one 10th less than that of any other cell in the body, so it happens quite rarely in those cells that would pass on those mutations to their offspring.

Chris - Ah, so the body's defending against that happening as best it can. But eyelids are regarded as less of a priority.

Hannah - That's true.