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Finally back for some discussion of saber-tooth cats, nimravids, and barbourofelids. There are two complementary articles that appeared almost simultaneously regarding the shape of the saber-tooth skull. Skull shape was examined by mapping various landmarks on different species’ skulls and measuring the change in position of these landmarks compared to average values.
I’ve been much delayed, since I am starting to work seriously on my dissertation. This sucks up an amazing amount of brainpower. Initially I was planning on delaying this post another day, but have now been fortified with a BLT (heavy on the bacon) and am ready to tackle the topic. It is one that interests me because it combines two fascinating topics, malaria and sex ratios.
Just a quick round-up of some links. On the same day I wrote about Gerobatrachus hottoni PZ Myers at Pharyngula also posted regarding the transitional amphibian, including a beautiful photograph of the fossil. I also logged in a few days ago to find to my surprise that my recent post on the non-necessity for mice of some genes that are required in humans was included in the Gene Genie blog carnival. This blog carnival covers human genetics, usually focusing on the field of medicine. Medicine is another interest of mine (I skim New England Journal of Medicine and The Lancet weekly), but since this blog is focusing on evolutionary biology I haven’t covered medicine much here, and it hadn’t occurred to me that post would meet inclusion in Gene Genie! You can read the current Gene Genie at Highlight Health. I also read the medicine-themed blogs Denialism and Respectful Insolence, so check those out if medicine interests you.
I checked in on Nature earlier, since a new issue comes out tomorrow, and find that there’s an article combining two favorite topics of mine—malaria and sex ratios. I can only read the abstract from home, so I hope the suspense doesn’t keep me up too late. I anticipate that paper will show up on my blog shortly.
ANIMAL MODELS are widely used in medical research, sometimes in testing new drugs for safety before human trials, other times as model systems for human diseases. Like all mammals, humans and mice share most of their genes, and maintain high sequence similarity. These factors suggest that many of these genes should share the same role. A new study in Proceedings of that National Academy of Sciences examines this hypothesis.
We’ve had a blitz of platypus genome papers this week, with a brand new article on the platypus genome sequence in Nature and several papers on specific aspects of this genome showing up in Genome Research. I hope to cover a couple of these in the next week. It’s been a while since my last update because I’ve been very busy, but I’ll take a look at the platypus genome paper itself tomorrow and hopefully follow-up Sunday or Monday with some of the information from Genome Research.
Of course this discovery has led to more bad reporting, and from reading the news outlet articles it looks like the scientists involved are contributing to some of it! Some of the things they are saying are not wrong, but possibly misleading. I’ll go into that a little bit tomorrow. For now let’s say I keep seeing the word “primitive”, and the New York Times refers to monotremes as “offshoots of the main mammalian lineage”. Well, I personally think the placentals and marsupials are branches off that most noble main mammalian lineage, the sadly extinct multituberculates.
THE MICROVIRUSES are positive-strand DNA viruses with very small genomes, typified by ΦX174 with 5,400 base pairs and nine genes. Cramming this many genes into that short a sequence requires overlapping reading frames, with gene B contained inside gene A, and gene E contained inside gene D.1 These nested genes are frame-shifted compared to the gene that contains them.
I COVERED the volvocine algae recently and promised a post on some of the genes involved in the evolution of multicellularity in this group. We still know relatively little about the genomes of volvocine algae, but research has picked out three genes involved in the evolution of multicellularity. These are invA, glsA, and regA.
MOST OF OUR study of gene networks has been done by comparison of related species to reconstruct network evolution and by knocking out specific genes to determine what the effects of their absence are. In a new paper Isalan and coworkers try something new, reprogramming genetic networks in Escherichia coli and examining the mutants to detect viability and any possible benefits to genetic pathway modification.
LOTS OF GOOD stuff appearing in the blogosphere this past week. PZ Myers has a post on how chromosome counts change and can contribute to speciation. Emile writes about beetles that chemically enslave ants. On the paleontological side of things Darren Naish wraps up his series on British cat species and Brian Switek reports on a new study showing that elephants are descended from aquatic ancestors, with links to blog coverage at other sites.
I will post tomorrow about the results of an experimental addition of links to gene networks in bacteria and later this week a survey of some of the genes involved in developing multicellularity in volvocine algae.
IN MANY CASES even large phenotypic changes can occur without much genetic change. However, occasionally a species will be placed in a situation in which its ancestor’s genes are insufficient, and if the species possesses a gene that can be co-opted into a new role, selection can favor evolution of new genes and a corresponding radiation of species. The Pieridae family of butterflies lay their eggs on plants in the Brassicaceae family, which contains mustards and cabbages. These plants have evolved to produce compounds that are harmless in undamaged leaves, but when a leaf is damaged are converted to a potent insecticide. The pierids evolved a deactivating protein that diverts the chemical reaction to produce nontoxic products. This gene evolved shortly after the plants themselves, and would have allowed these butterflies’ larvae to feed upon these plants with little competition.