Figure 1. Evolutionary fates of a duplicated gene pair within a protein interaction network.

After a single gene duplication event, the two duplicate genes are thought to assume one of several fates (Conant and Wolfe, 2008): (a) The most likely outcome is that one gene will be silenced by pseudogenization; alternatively, if both genes are preserved, this may be (b) owing to selection for increased dosage (c) because they acquire complementary deleterious mutations in independent subfunctions such that both are required to produce the full set of ancestral function (subfunctionalization), or (d) because one gene may acquire a new function (neofunctionalization).