But what connects these ancient genetic parasites with the structure of eukaryotic genes? Little more than the detailed mechanism of the RNA scissors that splice out mobile bacterial introns, and simple logic. I mentioned the spliceosomes a few paragraphs ago: these are the protein nanomachines that cut out the introns from our own RNA transcripts. The spliceosome is not only made of proteins: at its heart is a pair of RNA scissors, the very same. These splice out eukaryotic introns by way of a telltale mechanism that betrays their ancestry as bacterial self-splicing introns (Figure 27).
