I was talking about evolution with some students the other day and one of them said, 'But to get new features in an organism you have to have new genes, and mutation can't do that." We talked a bit about transposons and other means of gene duplication, & I also pointed out that changes in the control regions for a gene – & not the gene itself – could also have far-reaching consequences in terms of form and function. But I didn't have a specific example to hand. Until today.
Until today, when I happened upon a couple of reviews of recent research projects looking into just that – the impact of changing a control region on the expression of a gene, and subsequently on form &/or function of the organism. They're great reviews & I'm not going to try to do another one myself, I'll just introduce these two.
The first is on Darwin's tomatoes. I didn't know that Darwin brought back tomato specimens from the Galapagos, but he did, & they've spurred quite a lot of research since. The two species he brought back live in different habitats, but are capable of interbreeding. And although they look quite different, that difference is due to a single base-pair deletion in the control region for a gene. For the full story, read Stephen Matheson's post on his blog, Quintessence of Dust.
And the other item is about bats' wings and mouse legs. Although the underlying skeletal features are homolgous, the actual limbs look rather different, don't they? But guess what – if you replace one of the leg-form control sequences in a mouse forelimb with the homologous sequence from a bat… you get a mouse with longer forelimbs than normal. How cool is that?? Matheson writes about this one as well.
Go on, open the links & read these stories – this is cutting-edge stuff and so exciting for what it implies about the development of evolutionary novelty.