Genes jump from snakes to cows

10 January 2013

Interview with

Nell Barrie

Kat - But first, it's time to take a look at the top stories from this month with science writer Nell Barrie.  What have you got for us this month, Nell?

Nell - So, we've got one study that is very interesting and it's looking at how a quarter of the cow genome actually came from snakes or is this really true? That's the question. This is in the Proceedings of the National Academy of Sciences by Ali Morton Walsh and her team at the University of Adelaide.

Kat - Now, this is a bit crazy because cows and snakes aren't really related, so what is this? What is this bit of their genome?

Nell - Exactly, so you kind of immediately look at this and go, "What? How on earth could that be possible? That's ridiculous!" And it's looking at a piece of DNA which is called Bovine B or BovB sequences. And what they found is that about a quarter of the cow DNA sequence is made up of this BovB. The really interesting thing is it's not just in cows. It's in lots of other animals as well and the question is, how did it get there?

Kat - Because they thought this was something really distinct for cows. They have this repetitive thing that's for cows.

Nell - Exactly, and the idea would be that if you've got this repetitive sequence in cows, if you look in cows' relatives, closer relatives of the cows should have similar levels of this repetitive sequence, but that wasn't what the researchers found.

Kat - What other sorts of animals have got this thing?

Nell - So, there actually loads of different animals and if you look at the kind of family tree of this gene sequence, you find all these really odd things where it seems like cows are actually closer to snakes than they are to elephants, and there's a gecko that seems to be very closely linked to horses with the amount of this DNA sequence, much more closely than it is to other lizards. So, you're looking at this thinking, this just can't be possible. These results must be wrong. It's really weird.

Kat - So, either Darwin was completely wrong, evolution isn't true, or there's something else. What do they think is going on here? This is nuts!

Nell - Well, we think Darwin wasn't wrong, so that's a relief at least, but what it appears to be is that these are what are called jumping genes. So they're genes that can literally take themselves into the genome, copy themselves all around. They're really, really good at doing this but the question is, how have they got between these different species and the answer could be, something as simple as a tick. So parasitic insects that can actually go between say, a lizard and a cow, and transfer these genes in that way, so it's pretty crazy stuff.

Kat - This sounds pretty controversial to me.

Nell - Well, yeah that's exactly right and I mean certainly, it's not what you'd assume from these results. I mean, I guess the logical thing you'd say is something has gone wrong with these results somewhere and of course, it's always very difficult to do this kind of sequencing.

So, if you're thinking of people who work in a lab, all these different DNA sequences, there's always that possibility of contamination. But the researchers were very, very careful about this because obviously, they recognise that was a huge possible problem. So, it seems that that wasn't the case, but we are going to need some more work to find out really what's going on, and how exactly these genes manage to transfer themselves and spread so quickly. So, it seems like that would be a really rare event for this kind of tissue to sneak through somehow, but clearly, something weird is going on, so it's very interesting.

Kat - Or maybe it's really common and we just haven't found any other ones yet.

Nell - That could also be the case and we know that this does happen a lot, so there's this thing called horizontal gene transfer which happens a lot in bacteria. But, it seems like it could happen in much larger animals as well, so that is really fascinating.

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