Practice question

Multigene families are classified based on sequence similarity and organization. Simple or identical families consist of clustered, tandemly repeated genes encoding functionally identical products required in high dosage, lacking significant divergence. Ribosomal RNA genes at NORs exemplify this, comprising hundreds of identical transcription units encoding 45S precursor processed into 18S, 5.8S and 28S rRNAs. Concerted evolution via unequal crossing over and gene conversion maintains sequence homogeneity. In contrast, complex families like globins or MHC display divergent paralogs encoding related but distinct proteins with specialized functions across tissues.