On We Beasties, Kevin Bonham tells us all his thoughts on GoD—the Generation of Diversity that enables B-cells “to make antibodies that recognize almost any chemical structure that has ever existed or will ever exist.” By recombining three essential pieces of an antibody (with 100, 30, and 6 variants respectively), using enzymes to slice up DNA and stitch it back together, and owing to a little extra variation from our parents and a dash of random nucleotides, B-cells can fabricate about 10 billion different antibodies to intercept viruses, bacteria, and other intruders. On ERV, Abbie tells us that the same antibody can come in five different forms, or isotypes, that fill functional niches in a total immune response. Abbie writes, “Because your immune system is mindless […] this ends up generating a lot of waste, like many evolved systems.” But “it also means youve got a lot of bases covered when you are exposed to a new pathogen.”
On Not Exactly Rocket Science, Ed Yong reports that two new human genomes have been sequenced: that of South African leader Desmond Tutu, and that of !Gubi, a tribal hunter-gatherer. Along with !Gubi, researchers examined the genes of three other Bushmen, and the diversity they observed was “astounding.” Ed writes that there is more genetic variation between any two of these individuals than there is between “a European and an Asian,” and trying “to understand human genetics without understanding Africa is like trying to learn a language by only looking at words starting with z.” On Gene Expression, Razib Khan explains that “all non-Africans likely descend from one migration Out of Africa, so they carried with them only a small proportion of the total genetic variation of the ancient Africans because of the population bottleneck to which they were subjected.” And back on Not Exactly Rocket Science, Ed Yong introduces us to the ancient Inuit “Inuk,” the ninth human to have his genome sequenced before Tutu and !Gubi became ten and eleven.
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On Laelaps, Brian Switek considers the fate of Smilodon, a saber-toothed hypercarnivore that roamed through ancient Los Angeles. Although textbook descriptions of such animals are usually cut-and-dried, Brian writes that “genetic, anatomical, or behavioral variations are grist for natural selection’s mill,” and so individuals within a species can vary considerably over space and time. On Tetrapod Zoology, Darren Naish discusses the peculiar babirusa, a beast that looks like a pig, incorporates “deer-like slender legs and a multi-chambered stomach,” and has horn-like canine teeth growing from its snout. Babirusas display a wide range of morphology across their Indonesian habitat—and a male babirusa even begat hybridized offspring with a domestic pig in a zoo. Finally, on Gene Expression, Razib Khan reports new efforts to raise the Aurochs from the dead. Using preserved genes as a guide, breeders will “hunt for the variants in modern cattle strains” in an attempt to recreate the phenotype and genotype of this extinct piece of meat.
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Continue reading “Variations on a Theme”