Complex multigene families show:
Complex multigene families evolve through repeated duplication followed by functional divergence under selection for novel functions. Unlike simple families maintained by concerted evolution, complex families accumulate non-synonymous substitutions leading to related but distinct sequences retaining recognizable homology while exhibiting variation in expression pattern, ligand binding or catalytic specificity. Beta-globin, olfactory receptor, immunoglobulin variable regions and HOX families illustrate related yet divergent paralogs arranged in clusters with locus control regions. Introns and flanking sequences diverge more rapidly, while key functional domains preserve ancestral motifs.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 4: Complex Multigene Families Related but Divergent Sequences