Evolutionary Scrap-heap Challenge: Antifreeze Fish Make Sense Out Of Junk DNA

Science Daily reports Evolutionary Scrap-heap Challenge: Antifreeze Fish Make Sense Out Of Junk DNA

Scientists at the University of Illinois have discovered an antifreeze-protein gene in cod that has evolved from non-coding or ‘junk’ DNA. Since the creation of these antifreeze proteins is directly driven by polar glaciation, by studying their evolutionary history the scientists hope to pinpoint the time of onset of freezing conditions in the polar and subpolar seas. Professor Cheng will present her latest results at the Annual Main Meeting of the Society for Experimental Biology in Canterbury on Tuesday the 4th April

Hattip Pete Dunkelberg

The abstract reads

Old proteins and DNA, new tricks: Molecular evolution of antifreeze proteins in polar fishes

C.Cheng (University of Illinois)

Hyposomotic marine teleost fishes endemic to icy, freezing polar or subpolar waters face constant threat of freezing death. This was overcome in various species by the evolution of novel antifreeze proteins (AFPs), which bind to incoming ice crystals and arrest their growth, thereby preventing organismal freezing. The conventional paradigm of molecular evolution of novel proteins predicates on the “recycling” of pre-existing protein genes from which new genes arose under natural selection. Expectedly, by meaningful sequence similarities, four of the known AFPs (type II, III, IV and V) have inferred protein ancestors of unrelated functions, but presumably possessed structural elements with incipient affinity for ice and became selected upon. The genes of these AFPs arose from simple duplication of their respective ancestral gene (or gene domain), and the protein acquired robust ice-binding properties through cold-driven evolutionary tinkering of the coding sequence. A remarkable twist to this conventional gene-duplication/sequence-divergence paradigm is the creation of a unique functional antifreeze glycoprotein (AFGP) sequence from partly non-coding DNA in Antarctic notothenioid fish, involving de novo duplications of a 9-nt sequence spanning an exon-intron junction of an ancestral trypsinogen-type protease gene to form a large, highly repetitive (ThrAlaAla)n coding region, and shedding most of the protease gene structure. More remarkably yet, and apparently defying the old-to-new protein evolution paradigm is the independent genesis of the northern cod AFGP, which appeared to have drawn on entirely non-coding DNA for de novo expansion to form the repetitive AFGP coding sequence, creating sense from non-sense DNA.

Dr Cheng’s website provides access to much of her research publications.

The evolution of antifreeze in fish has been a well described example of gene duplication divergence and exxon shuffling and even convergent evolution, now it seems that the gene responsible for the anti-freeze in fish evolved from ‘junk DNA’.

Please remind me again: How does Intelligent Design explain all this?