So, I have recently become aware that Genomicron is cited on an intelligent design wiki entry for “junk DNA“. They quote two paragraphs from my post A word about “junk DNA”. Specifically, a paragraph in which I critique the term “junk DNA” as unnecessarily implying non-function for all non-coding DNA, and a paragraph in which I list many (unsubstantiated) hypotheses about universal functions for non-coding DNA. Here are two paragraphs from the post that they don’t quote:
To satisfy this expectation, creationist authors (borrowing, of course, from the work of molecular biologists, as they do no such research themselves) simply equivocate the various types of non-coding DNA, and mistakenly suggest that functions discovered for a few examples of some types of non-coding sequences indicate functions for all (see Max 2002 for a cogent rebuttal to these creationist confusions). Case in point: a few years ago, much ado was made of Beaton and Cavalier-Smith’s (1999) titular proclamation, based on a survey of cryptomonad nuclear and nucleomorphic genomes, that “eukaryotic non-coding DNA is functional”. The point was evidently lost that the function proposed by Beaton and Cavalier-Smith (1999) was based entirely on coevolutionary interactions between nucleus size and cell size.
Does non-coding DNA have a function? Some of it does, to be sure. Some of it is involved in chromosome structure and cell division (e.g., telomeres, centromeres). Some of it is undoubtedly regulatory in nature. Some of it is involved in alternative splicing (Kondrashov et al. 2003). A fair portion of it in various genomes shows signs of being evolutionarily conserved, which may imply function (Bejerano et al. 2004; Andolfatto 2005; Kondrashov 2005; Woolfe et al. 2005; Halligan and Keightley 2006). On the other hand, the largest fraction is comprised of transposable elements — some of which become co-opted by the host genome, some of which play major role in generating genomic variation, some of which may be involved in cellular stress response, and yet others of which remain detrimental to host fitness (Kidwell and Lisch 2001; Biémont and Vieira 2006). The upshot is that some non-coding DNA is most certainly functional — but when it is, this usually makes sense only in an evolutionary context, particularly through processes like co-option. More broadly, those who would attribute a universal function for non-coding DNA must bear the following in mind: any proposed function for all non-coding DNA must explain why an onion or a grasshopper needs five times more of it than anyone reading this sentence.
Funny that my post Function, non-function, some function: a brief history of junk DNA, in which I discuss how anti-evolutionists are wrong about the history and the science of non-coding DNA, is not quoted.
Here’s a quote they are welcome to use: Simply saying “junk DNA will turn out to have a function” is not a scientifically actionable prediction unless you specify what that function will be and a way to test the proposed function.