Figure 3.

Proposed scenario for the evolution of KCNA genes and clusters in vertebrates. Based on our analyses we suggest that all KCNA genes are derived from an ancestral intronless gene, as all genes included from Branchiostoma floridae are intronless and that KCNA7 in vertebrates independently gained an intron. Two tandem duplications led to the three gene clusters found in today's genomes, which was probably duplicated initially before the origin of the gnathostomes. Probably this is linked to the second genome duplication (2R) during vertebrate evolution. The four clusters in teleost fish originated through the fish-specific genome duplication (FSGD, 3R).