The naming of zebrafish genes required further genomic analyses in order to determine whether duplications originated from the ray-finned lineage whole-genome duplication event. Many of the duplicated genes reside within close proximity on the same chromosome, suggesting that they are segmental duplications that resulted from misguided recombination processes during meiosis and not a product of the whole genome duplication that took place within the ray-fin lineage [27]. These include the aldh2, aldh5a1 and aldh18a1 paralogues, which are located in close proximity on Chr 5, 16 and 12, respectively. It also includes aldh3a2.1 and aldh3a2.2, located on Chr 15, as well as aldh9a1.1 and aldh9a1.3, found on Chr 8. The gene architecture surrounding aldh3a2.3 on Chr 21 does not support a duplicated chromosome, in that the region lacks other duplicated genes from Chr 15. Furthermore, studies looking at zebrafish gene duplications found that a high frequency of genes found on Chr 21 are duplicated on Chr 5 and none were identified on Chr 15, suggesting that Chr 5, rather than Chr 15, is the paralogous chromosome [28,29]. A similar situation was
