A Response to Dr. Dawkins' "The Information Challenge" (Part 3): The "Junk"-DNA Blunder - Evolution News & Views

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A Response to Dr. Dawkins' "The Information Challenge" (Part 3): The "Junk"-DNA Blunder

[Editor's note: This was the third installment of a three-part series. The full article, A Response to Dr. Dawkins' "The Information Challenge", can be read here.]

In Part 1 and Part 2 of this response to Richard Dawkins' article, "The Information Challenge," I explained why gene duplication is not an adequate explanation of how Darwinian processes can produce new information. But Dawkins' article has other problems. He writes that "most of the capacity of the genome of any animal is not used to store useful information." This is another good example demonstrating how Neo-Darwinism led may scientists to wrongly believe that non-coding DNA was largely junk. Dawkins' statement is directly refuted by the findings of recent studies, which the Washington Post reported that scientists have now found that "the vast majority of the 3 billion 'letters' of the human genetic code are busily toiling at an array of previously invisible tasks." That strikes a fatal blow to Dawkins' argument:

 Dawkins then (1998)Scientists now (2007)
Position regarding "Junk"-DNA:"most of the capacity of the genome of any animal is not used to store useful information""the vast majority of the 3 billion 'letters' of the human genetic code are busily toiling at an array of previously invisible tasks"

Dawkins claims that there is "lots of repetitive nonsense" in the genome. But is it really "nonsense"? Recent studies are finding increasing function for allegedly non-functional repetitive DNA. Richard Sternberg surveyed the literature and found extensive evidence for function in repetitive DNA (also called repetitive elements, or "REs"). A listing of functions for REs reprinted from Sternberg's paper is shown below:

  • satellite repeats forming higher-order nuclear structures;
  • satellite repeats forming centromeres;
  • satellite repeats and other REs involved in chromatin condensation;
  • telomeric tandem repeats and LINE elements;
  • subtelomeric nuclear positioning/chromatin boundary elements;
  • non-TE interspersed chromatin boundary elements;
  • short, interspersed nuclear elements or SINEs as nucleation centers for methylation;
  • SINEs as chromatin boundary/insulator elements;
  • SINEs involved in cell proliferation;
  • SINEs involved in cellular stress responses;
  • SINEs involved in translation (may be connected to stress response);
  • SINEs involved in binding cohesin to chromosomes; and
  • LINEs involved in DNA repair.

    (Richard Sternberg, "On the Roles of Repetitive DNA Elements in the Context of a Unified Genomic-- Epigenetic System," Annals of the New York Academy of Sciences, Vol. 981:154--188 (2002).)
  • Dawkins not only got repetitive junk-DNA wrong, he provides a shimmering example of the fact that neo-Darwinism has led many scientists to wrongly presume that junk-DNA has no function. Some Darwinists have tried to counter that claim by arguing that Neo-Darwinism also led other biologists to presume function for junk-DNA, since its mere presence in the genome implies that natural selection has preserved it for some purpose. Even if that were a good argument, the fact remains that the false junk-DNA mindset was born and bred out of the Neo-Darwinian paradigm. That paradigm misled many scientists on this point, and in fact continues to mislead them.

    But it isn't even clear that Darwinists have a good scientific justification to believe that junk-DNA, if it exists, would be naturally selected out of the genome. According to the 2006 edition of Voet and Voet's Biochemistry, there is insufficient selection pressure on functionless repetitive "junk"-DNA to remove it from the genome:

    No function has been unequivocally assigned to moderately repetitive DNA, which has therefore been termed selfish or junk DNA. This DNA apparently is a molecular parasite that, over many generations, has disseminated itself throughout the genome through transposition. The theory of natural selection predicts that the increased metabolic burden imposed by the replication of an otherwise harmless selfish DNA would eventually lead to its elimination. Yet for slowly growing eukaryotes, the relative disadvantage of replicating an additional 100 bp of selfish DNA in an 1-billion-bp genome would be so slight that its rate of elimination would be balanced by its rate of propagation. Because unexpressed sequences are subject to little selective pressure, they accumulate mutations at a greater rate than do expressed sequences.

    (Donald Voet and Judith G. Voet, Biochemistry, pg. 1020 (Jon Wiley & Sons, 2006), emphasis added.)

    In other words, Darwinists like Dawkins had every reason to presume that non-coding repetitive DNA was, in Dawkins' words, functionless "nonsense" that was, in Voet and Voet's words, a "molecular parasite," even though it persisted in the genome. But Voet and Voet are wrong to presume that such repetitive DNA is mere parasitic junk, given that examples of functions for it abound. Sternberg's article concluded that "the selfish DNA narrative and allied frameworks must join the other 'icons' of neo-Darwinian evolutionary theory that, despite their variance with empirical evidence, nevertheless persist in the literature." Sternberg, along with geneticist James A. Shapiro, concludes elsewhere that "one day, we will think of what used to be called 'junk DNA' as a critical component of truly 'expert' cellular control regimes." (Richard Sternberg and James A. Shapiro, "How Repeated Retroelements format genome function," Cytogenetic and Genome Research, Vol. 110:108--116 (2005).)

    It looks like Dawkins has some work to do if he is to update all of his arguments against ID and answer "The Information Challenge."


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