Bits and pieces Quote by Siddhartha Mukherjee

““As an anology, consider the word structure. In bacteria, the gene is embedded in the genome in precisely that format, structure, with no breaks, stuffers, interpositions, or interruptions. In the human genome, in contrast, the word is interrupted by intermediate stretches of DNA: s...tru...ct...ur...e. The long stretches of DNA marked by the ellipses (...) do not contain any protein-encoding information. When such an interrupted gene is used to generate a message-i.e., when DNA is used to build RNA-the stuffer frragments are excised from the RNA message, and the RNA is stitched together again with the intervening pieces removed: s...tru...ct...ur...e became simplified to structure. Roberts and Sharp later coined a phrase for the process: gene splicing or RNA splicing (since the RNA message of the gene was "spliced" to removed the stuffer fragments). At first, this split structure of genes seemed puzzling: Why would an animal genome waste such long stretches of DNA splitting genes into bits and pieces, only to stitch them back into a continuous message? But the inner logic of split genes soon became evident: by splitting genes into modules, a cell could generate bewildering combinations of messages out of a single gene. The word s...tru...c...t...ur...e can be spliced to yield cure and true and so forth, thereby creating vast numbers of variant messages-called isoforms-out of a single gene. From g...e...n...om...e you can use splicing to generate gene, gnome, and om. And modular genes also had an evolutionary advantage: the individual modules from different genes could be mixed and matched to build entirely new kinds of genes (c...om...e...t). Wally Gilbert, the Harvard geneticist, created a new word for these modules; he called them exons. The inbetween stuffer fragments were termed introns.””

— Siddhartha Mukherjee