Happy 70th birthday this week, genetic code!

by Matthew Cobb

Monday was my birthday, but Tuesday was the birthday of the idea of a ‘genetic code’. The first clear suggestion that genes contain a ‘code’ was made by the Nobel Prize-winning physicist Erwin Schrödinger on 5 February 1943, in Dublin. This was one of his key contributions to biology, which he made in a series of three public lectures that were published in 1944 under the title What Is Life?

As I have explained in a post at The Guardian:

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.

Most of the post deals with the way that ‘code’, cybernetics and information theory fed into the scientific mainstream, culminating in a momentous sentence 10 years later, in May 1953:

Ten years after Schrödinger’s brilliant insight, Watson and Crick’s second 1953 article on the structure of DNA provided the world with the key to the secret of life, casually employing the new concepts that had been created by cybernetics and propelling biology into the modern age with the words: “it therefore seems likely that the precise sequence of the bases is the code which carries the genetical information.”

These prophetic words – shorn of the conditional opening phrase – are uttered in biology classes all over the world, every single day.

Head on over to The Guardian to learn more. There are no jokes about cats in the article, I’m afraid, although there are plenty in the comments…

17 Comments

  1. Marcoli
    Posted February 7, 2013 at 9:38 am | Permalink

    This all seems pretty straightforward, at least in that some standard textbook answers will do the job here.
    1) Natural selection can only really select ‘against’ a trait, it does not directly select ‘for’ particular traits.
    2) Stabilizing selection was applied to the birds with extreme traits. Different traits were being selected against (wings too long / wings too short, etc.) Stabilizing selection more generally applies when an environment is stable, and the population has been optimized to that environment.
    3) If conditions change, or if a new environment opens up that becomes populated, NS will select against varieties that are less fit in that new environment — even if they were once the more fit. I am reminded of selection against finches with smaller beaks during droughts on the Galapagos — those finches are reasonably fit during times without drought. The result is directional selection. The average of the population shifts toward the more fit b/c of selection against the less fit.
    4) How does any of this lead to anything NEW? The standard answer, which seems adequate to me, is that sometimes directional selection is applied toward REPURPOSING structures for a new use. This is called EXAPTATION.

    • Posted February 8, 2013 at 8:57 am | Permalink

      Natural selection can only really select ‘against’ a trait, it does not directly select ‘for’ particular traits.

      Shirley, this can’t be right.

      Say you’ve got a weed growing in your crops and you spray it with glyphosate (Roundup). For plants, it’s a nasty poison.

      Now say there’s a random mutation in one of those weeds that permits it to metabolize glyphosate. It survives and multiplies.

      How is that not an example of natural selection for the novel ability to metabolize glyphosate?

      Indeed, methinks you’ve got it primarily backwards. While the selection against particular traits is certainly the most common occurrence, if one considers that a random mutation is more likely to be deleterious than beneficial. But it’s the differential selection of beneficial novel traits that’s the defining characteristic of Darwinian evolution.

      Cheers,

      b&

      • Posted February 8, 2013 at 8:57 am | Permalink

        …and it would be really nice if I could see that I hadn’t checked the checkbox before posting rather than in the instant after clicking the button and seeing the page refresh….

        b&

  2. Reginald Selkirk
    Posted February 7, 2013 at 10:00 am | Permalink

    Happy 70th birthday this week, genetic code!

    Wha? I thought the genetic code was at least 3 billion years old. I know the YECs say < 10000. You're the only person I know who has declared it to be a hundred times younger than the YECs do.

    • Dave
      Posted February 7, 2013 at 6:33 pm | Permalink

      :-)

  3. Posted February 7, 2013 at 10:15 am | Permalink

    Y CELEBRATE SOMETHIN AS DEGENERATE AS TEH GENETIC CODE?

  4. Posted February 7, 2013 at 11:44 am | Permalink

    Dr. Cobb’s fine Guardian article continues: “But in 1947 there was a missing component in biological thinking about the nature of the code, one which was at the heart of Watson and Crick’s decisive interpretation of their discovery a mere six years later – “information”. That idea entered biology through some applied research carried out to aid the war effort.”

    Actually, if you translate “information” as “stored information”, then you get to “memory.” DNA is our genetic memory. In this context, the information idea was introduced to biology in 1870 by Ewald Hering in Prague. His German text was brought to the attention of the English-speaking world by Edwin Ray Lankester (1876 Nature) when commenting on a monograph of Ernst Haeckel. The idea was independently introduced to English-speaking readers by Samuel Butler in a series of evolution books that began with “Life and Habit” (1878). Traces of the information idea can also be discerned in Butler’s earlier science fiction work “Erewhon” (1872).

  5. Gregory Kusnick
    Posted February 7, 2013 at 1:06 pm | Permalink

    Slight nitpick:

    I’ve always understood “the genetic code” to refer not to the raw sequence of base pairs in DNA, but to the mapping of codons into amino acids embodied by tRNA (and Wikipedia seems to agree with me).

  6. Matthew Cobb
    Posted February 7, 2013 at 2:01 pm | Permalink

    Well if Wikipedia says so.. ;)

    The point is that Schrödinger was the first to *explicitly* suggest there was a ‘code’ in genes, as I explained in the Guardian article.

    The 50th anniversary of the cracking of ‘the’ genetic code by Nirenberg and Matthaei was in 2011, as I described here:

    http://www.telegraph.co.uk/science/science-news/8546830/Genes-and-DNA-meet-the-first-man-to-read-the-book-of-life.html

    • whyevolutionistrue
      Posted February 7, 2013 at 4:30 pm | Permalink

      congrats, Dr. Cobb; is this your first Guardian column. Nicely written!

      jac

      • shazam
        Posted February 7, 2013 at 4:45 pm | Permalink

        Hah! I beat you to it, JAC… Does this get me an autographed copy of WEIT? (whispers Henri in vague French accent)

  7. shazam
    Posted February 7, 2013 at 4:24 pm | Permalink

    Congratulations on what would seem to be your first contribution to The Guardian.

  8. Dave
    Posted February 7, 2013 at 6:34 pm | Permalink

    How about that Schrödinger – H wave functions AND the genetic code!

  9. Jim Thomerson
    Posted February 8, 2013 at 1:34 pm | Permalink

    Three later workers rediscovered, credited, and publicized the work of Mendel. They were De Vries, Correns, and Tschermak (1871-1962). Of the three, Tschermak lived to see the reading of the genetic code, initiated in 1961, as mentioned in the post. It is remarkable that a man responsible for starting modern genetics would live to see the reading of the code. How rapidly we have progressed.


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