Gene duplications, and whole (or larger parts of) genome duplications in particular, are considered to be the main force by which gene repertoires increase; because of a duplication event, one of the two gene copies can, on occasion, acquire a new function, whereas the other copy remains to fulfil the ‘original’ task. In general, if the two paralogues fail to differentiate their functions or their spatial or temporal expression patterns , one of the two paralogues will disappear as a result of redundancy