Some mistakes turn out to be beneficial. And life, or its survival, has always thrived on them. Add a few mutations to a genome, drench it in time, and you have the driving force of evolution. Transposons - these bits of DNA that are able to skip along genomes - are just one kind of mutation that has contributed hugely towards life's unfolding. Not so long ago, researchers discovered remnants of a well-known transposon, made up of so-called mariner elements, glued aside another gene whose product is a histone methyltransferase. This chimeric gene, baptised SETMAR, expresses a product whose roles are similar to both of its parts. But with a little twist. A twist which, in the past 50 million years, has contributed to human evolution, and is due to the protein it expresses: histone-lysine N-methyltransferase SETMAR.
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