Pseudogenes Are Pseudogenes and They Are Almost Always Junk

The IDiots have found a paper by Wen et al. (2012) with a very provocative title, "Pseudogenes are not pseudo any more."

Naturally, lawyer Casey Luskin is all over this: Paper Rebuffs Assumption that Pseudogenes Are Genetic "Junk," Claims Function Is "Widespread". And just as naturally, the folks at Uncommon Descent (probably lawyer Barry Arrington) jump on the bandwagon: Junk DNA: Yes, paper admits, it WAS thought to be junk.

The authors of the paper, including Templeton Prize winner Francisco J Ayala, claim that pseduogenes exhibit two puzzling properties: (a) similar processed pseudogenes occur in mouse and humans suggesting that they are conserved, and (b) many pseudogenes are transcribed.

Processed pseudogenes arise when mRNA transcripts are reverse transcribed and inserted back into the genome. They usually come from genes that are highly expressed in germ line cells. Such genes tend to be highly conserved in related species. Mammals are closely related on the scale that were talking about. It's not surprising that a few new pseudogenes in such lineages are very similar in sequence. They're still pseudogenes. The vast majority of known pseudogenes are evolving at a rate that approximates the rate of mutation indicating that they are not constrained by negative selection.

Many pseudogenes are derived from gene duplications followed by mutations in one of the copies that make them incapable of producing a functional product. There's no reason to suspect that the first of these debilitating mutations will prevent transcription; therefore, one expects that many pseudogenes will be transcribed.

Some pseudogenes have been co-opted to provide a different function. There aren't very many examples but that doesn't stop the IDiots from making the fantastic leap from 0.0001% to 100%. (Pseudogenes represent about 1% of the genome [What's in Your Genome? ] so even if we assume that every single pseudogene is not a pseudogene, it hardly makes a dint in the amount of junk DNA.)

I discussed all this when I reviewed Jonathan Well's book The Myth of Junk DNA. The relevant chapter is Chapter 5 [Junk & Jonathan: Part 8—Chapter 5]. That review was posted in May 2011. It seems clear that the lawyers on the IDiot websites haven't read it.

Here's what one of them says on Uncommon Descent.

Darwin’s followers considered junk DNA powerful evidence for their theory, which is really a philosophy (often a cult), and that they often expressed that view, often triumphantly. Others insist it is true anyway.

The problem they hope to suppress is that if lots of junk in our DNA is such powerful evidence for their theory, then little junk throws it into doubt. That is, if it is such a good theory, why was it wrong on a point that was announced so triumphantly?

So it is a good thing that the science-minded public is reminded of the historical fact that Darwinism was supported by junk DNA. And it will be fun when the squirming editorials come out in science mags, warning people not to read too much into this, Darwin is still right.

I'm not even going to bother pointing out how stupid that is. If you're reading Sandwalk, chances are high that you could detect the lies¹ with your eyes closed.

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1. Yes, "lies." At this point there's no other explanation.

Wen, Y-Z., Zheng, L-L., Qu, L-H., Ayala, F.J., and Lun, Z-R. (2012) Pseudogenes are not pseudo any more. RNA Biology 9: 27 - 32. [doi: 10.4161/rna.9.1.18277]