ALDH2 appears to be one of many genes duplicated in zebrafish. It has been suggested that an entire genome duplication event may have occurred after the divergence of teleosts and mammals;[25] this may explain the increased ALDH gene number in zebrafish. A second gene-duplication event appears to have occurred, giving rise to three zebrafish aldh2 gene records (aldh2.1-3). The aldh2.1 gene is believed to be the parent, based on homology with orthologous ALDH2 protein sequences. Both aldh2.2 and aldh2.3 potentially encode full-length peptides. Aldh2.2 is 95.2 per cent similar to Aldh2.1 and aldh2.3 may represent a more evolutionarily recent duplication of aldh2.2, as evidenced by 99.6 per cent AA identity between the Aldh2.2 and Aldh2.3 proteins.
