May 16, 2008

More platypus

I've been poking about a little bit extra in the platypus genome for a week now in response to the platypus genome release article I wrote about in my previous post. It was a pleasant surprise to notice that so many of the gene families we are interested in in our lab have distinguishing features in the platypus. It has the neuropeptide Y7 receptor, which is absent from other mammals; it has a unique galanin receptor that I've been looking into some more; it has the shortwave-sensitive-2 opsin gene, the visual pigment that detects blue light, which is absent in other mammals (we have modified the ultraviolet-light-detecting opsin to see blue light instead)... it's pretty interesting stuff.

I missed this BBC article last week. It's not spectacular, but it has a nice audio interview with professor Jenny Graves at Australian National University, co-author of the genome release paper. I liked this highlight of what we are able to learn about evolutionary transitions by looking into and comparing genomes:

The platypus is a mammal, it makes milk and it has fur so it is defined as a mammal, but it left the rest of the mammals a long time ago. It diverged 166 million years ago from a common ancestor that probably looked more like a reptile than a mammal. So it's not a reptile, it is a mammal but it's retained a lot of reptilian characteristics like laying eggs for instance... Of course one of the things we wanted to look at was egg-laying and making milk because we want to retrace the steps in how did we get to be mammals? and so first of all we looked at the egg yolk proteins and indeed there is an egg yolk protein there, but there's only one of them whereas birds have three for instance. So it looks as though the platypus is already shifting its allegiance from nurturing their young inside an egg and nurturing their young with milk.

There have also been quite a few blog posts concerning the platypus, which is fun. Pharyngula and Adaptive Complexity both have very comprehensive posts and both also take issue with the purported image of the platypus as a composite creature, "part bird, part reptile, part mammal"; Genomicron and Nimravid focus on the problem with calling the platypus "primitive" or defining its characteristics as "reptilian" or "avian"; Carl Zimmer just wants to know where the platypus' stomach went and The Digital Cuttlefish shares with us a few inspired words.

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1 comment:

  1. like the look from your blog

    Saludos from Sevilla Spain


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