Figure 1.

Evolution of homeobox gene organization. Pollard and Holland [3] suggest that the current organization of Antennapedia-superclass homeobox genes might have occurred through the illustrated process of gene duplication, chromosome duplication, gene loss, and chromosome rearrangement. (a) The genes thought to have been linked into one cluster in the last common ancestor of all vertebrates. (b) Scenario of gene duplication (arrows), gene losses (white boxes) and losses of linkage (double slashes) proposed by Pollard and Holland [3]. Adapted from [3].