What is life? The physicist who sparked a revolution in biology

Guardian, By Matthew Cobb

Erwin Schrödinger introduced some of the most important concepts in biology, including the idea of a ‘code’ of life

Seventy years ago, on 5 February 1943, the Nobel prizewinning quantum physicist Erwin Schrödinger gave the first of three public lectures at Trinity College, Dublin. His topic was an unusual one for a physicist: “What is Life?” The following year the lectures were turned into a book of the same name.

One of Schrödinger’s key aims was to explain how living things apparently defy the second law of thermodynamics – according to which all order in the universe tends to break down. It was this that led my colleague Professor Brian Cox to use Schrödinger as the starting point of his BBC series Wonders of Life, leading to What is Life? shooting up the Amazon sales chart.

But Schrödinger’s book contains something far more important than his attempt to fuse physics and biology. In that lecture 70 years ago, he introduced some of the most important concepts in the history of biology, which continue to frame how we see life.

At a time when it was thought that proteins, not DNA, were the hereditary material, Schrödinger argued the genetic material had to have a non-repetitive molecular structure. He claimed that this structure flowed from the fact that the hereditary molecule must contain a “code-script” that determined “the entire pattern of the individual’s future development and of its functioning in the mature state”.

This was the first clear suggestion that genes contained some kind of “code”, although Schrödinger’s meaning was apparently not exactly the same as ours – he did not suggest there was a correspondence between each part of the “code-script” and precise biochemical reactions.

Historians and scientists have argued over the influence of Schrödinger’s lectures and the book that followed, but there can be no doubt that some of the key figures of 20th century science – James Watson, Francis Crick, Maurice Wilkins and others – were inspired to turn to biology by the general thrust of Schrödinger’s work.

The role of the brilliant “code-script” insight is less clear. Reviewers of What is Life? in both Nature and the New York Times noted the novel phrase, but despite the fact that in 1944 Oswald Avery published clear evidence that DNA was the genetic material, virtually no one immediately began looking for – or even talking about – a molecular “code-script” in DNA, although Kurt Stern suggested that the code might involve grooves in a protein molecule, like the grooves in a vinyl disc.

Part of the reason for this lack of immediate excitement and for Avery’s discovery not being widely accepted was that DNA was thought to be a “boring” molecule with a repetitive structure – exactly what Schrödinger had said a gene could not be. It took the work of Erwin Chargaff, inspired by Avery, to show that the proportion of the “bases” in the DNA molecule – generally presented by the letters A, T, C and G – differed widely from species to species, suggesting the molecule might not be so boring after all.

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