The DNA helix gave 20th-century biology its symbol. But the more we learn, the more life circles back to an older image
The DNA helix is important, of course. But the most important thing it does is make proteins that can operate in regulatory loops. These loops can also operate at the molecular level: genes make proteins, but these proteins determine which genes are ‘off’ and which are ‘on’ (as HIF1A does), making a control loop at even the molecular level. Unlike the helix, loops also operate at scales far above the molecular, covering a range of sizes from bacterial colonies to the vast ecosystems of the rainforest – perhaps to the ecosystem of the entire Earth. Beyond Earth, life without DNA is just about thinkable (one can imagine alternative strategies for storing information). Life without feedback loops, though? I have never met any biologist who can imagine that.
The helix is too well-established an icon to be deposed any time soon. And yet, a simple loop would be a much more universal symbol of how life works at all of its scales and levels. Perhaps the Ouroboros, beloved of gnostics and alchemists, has been an ideal symbol waiting in the wings for centuries: there can surely be no more evocative symbol of feedback than a snake growing by devouring its own tail.
Full article: A closed loop by Jamie Davies