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Genetic Strength in Numbers

On the Weizmann Wave, researchers have made a discovery surrounding exons—”bits of genetic code that are snipped out of the sequence and spliced together to make the protein instruction list.” When a cell needs to make a protein, it pulls exons out of pre-messenger RNA and stitches them together to form messenger RNA. Alternating sequences called introns are left out. By tracking the unused introns, researchers observed that “in some cases, pre-mRNA production shot straight up – to ten times or more than that of the mRNA that followed.” They call this “production overshoot,” for when “the cell needs a rush job on the manufacture of certain proteins.” On Pharyngula, PZ Myers tackles the phylogeny of modern primates. Although chimpanzees are our closest living relatives, 30% of the newly-sequenced gorilla genome is closer than chimp to human. This is the result of Independent Lineage Sorting, which Myers calls an expected outcome of evolution, not an obstacle to its acceptance. Myers says “The only way you would fail to see ILS is if every genetic difference between two species emerged simultaneously, in lockstep, in one grand swoop.” Like mRNA production, speciation in practice is a lot more messy.