Small fish genome yields big insights

Geneticists have decoded the smallest known vertebrate genome: that of the puffer fish Tetraodon nigroviridis. The fish's 21 chromosomes, which together contain more than 300 million letters of DNA, tell a twisting evolutionary tale and even shed light on our own genetic make-up.

Comparison with other genome sequences shows that fish proteins have diverged much faster than those in mammals, an international research group reports in this week's Nature. Included in this group are many researchers at the Broad Institute.

Tetraodon contains several key genes previously thought to be absent from fish, and also flags up some 900 previously unrecognized human genes.

Most genes in the human DNA sequence have two counterparts in the Tetraodon genome, the researchers add, showing that the ancestors of this fish must have undergone a genome duplication at some point. Indeed, the Tetraodon sequence may even give us a window on the last common ancestor of Tetraodon and humans — a primitive bony fish that lived hundreds of millions of years ago — according to an accompanying News and Views article.