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    Junk DNA and Complexity Science: A Sad mix
    By Michael White | May 21st 2010 02:56 PM | 7 comments | Print | E-mail | Track Comments
    About Michael

    Welcome to Adaptive Complexity, where I write about genomics, systems biology, evolution, and the connection between science and literature,

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    A quote from an extremely mediocre book, Complexity: A Guided Tour. Like most people coming out of the 'complexity sciences', the author has a mediocre grasp of molecular biology, both current developments, and the history of the field. It's frustrating that these network people keep hyping supposedly new revolutionary discoveries made the past 10 years of the genome era - discoveries, that in fact have been known for decades. For people clearly new to biology, molecular biology before the year 2000 was a big black hole of ignorance.

    There are several claims that make me angry in this book, but here's one claim that is like a zombie and refuses to die, no matter how many times it's been knocked down:

    Proponents of Evo-Devo propose that morphological diversity among species is, for the most part, not due to differences in genes but in genetic switches that are used to turn genes on and off. These switches are sequences of DNA - often several hundred base paris in length - that do not code for any protein. Rather they are part of what used to be called "junk DNA," but now have been found to be used in gene regulation...


    And then there's this excruciating passage:

    According to Evo-Devo, such modifications - in the parts of DNA long thought of as "junk" - are the major force in evolution, rather than the appearance of new genes. Biologist John Mattick goes so far as to say, "The irony... is that what was dismissed as junk [DNA] because it wasn't understood will turn out to hold the secret of human complexity.


    OK class, let's go over a little history:

    1972: The term 'junk DNA' is coined. It is not used to refer generally to non-coding DNA.

    1967: Mark Ptashne shows that a regulatory transcription factor (the lambda phage repressor) binds to non-coding DNA flanking the protein-coding genes.

    And the idea that genes are regulated by non-coding sequences was around well before that. Certainly long before Evo-Devo came on the scene.




    Second, John Mattick is clueless, and he should not be quoted. So junk DNA holds the secret to human complexity? Then I supposed it also holds the secret to the incredible complexity of an onion, which has five times more non-coding DNA than humans. Ryan Gregory came up with the onion test to counter the nonsense peddled about junk DNA:

    The onion test is a simple reality check for anyone who thinks they have come up with a universal function for non-coding DNA1. Whatever your proposed function, ask yourself this question: Can I explain why an onion needs about five times more non-coding DNA for this function than a human?



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    Comments

    kerrjac
    Interesting refute, looks like 'junk science'.
    Just out of curiosity tho, what's the standard explanation for junk DNA? Is it just structural or something?
    adaptivecomplexity
    Check out Ryan Gregory's series on the history of the term. There are really two things that bug me when this subject comes up: people say that junk DNA means something that it didn't originally mean (i.e., non-coding DNA), and they claim that until recently people thought that non-coding DNA had no function. Both claims are wrong, but still made by people who apparently aren't familiar with any molecular biology that came before the 1990's.
    Mike
    AdamRetchless
    A  lot of what I consider "junk" is selfish elements, such as transposons (and their corpses). I'm not sure if that's what other people call "junk", since it often encodes proteins.
    adaptivecomplexity
    That's a good, often neglected point. Junk DNA is not simply non-coding DNA.
    Mike
    I don't understand why John Mattick's stuff gets published in the scientific literature and in the popular science press.

    Seriously, peer review is supposed to be one of the cornerstones of science but there seem to be a lot of "peers' who wouldn't know a good logical argument if it bit them on the behind. There has to be something very wrong with modern molecular biology and biochemistry if people like Mattick are held up as examples of good scientists. Where did we go wrong and how can we fix it? Are blogs helping? (I think so.)

    Hank
    Are blogs helping? (I think so.)
    I think yours helps. And Mike's and plenty of others but it takes a bit of a sea change before popular science press and quality dovetail when even peer review can miss important things. One of the goals in setting up a site like this is to achieve a quality 'critical' mass where people know they can find insight that isn't dumbed down. It will take time but content is king and people want to be smarter.
    adaptivecomplexity
    I'm just as baffled as you are that John Mattick not only gets published, but also gets quoted in Nature news storied and books like this Complexity one.
    I do think blogs help - you and Ryan Gregory own this junk DNA topic on the blogs, and it's easy to find a comprehensive rebuttal to any nonsense claim about junk DNA by searching Sandwalk or Genomicron.
    Mike

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