A model of Ca2+ channel γ subunit gene family evolution. Integration of chromosome locations and molecular phylogeny data suggest a minimum of two tandem duplications of an ancestral γ subunit gene, followed by two duplications of the precursor of modern chromosome bands 16p11–p13, 17q11–q25, and 22q11–q24. Four potential genes suggested by the model (C′, C′′, A′, and A′′) but not identified in this study may have been lost during evolution sometime after the duplication indicated by arrow 3. Arrows 1 and 2 indicate tandem gene duplication events. Arrows 3 and 5 indicate regional (chromosome or whole genome) duplications. Letters (A, B,C) and symbols (′ , ′′) designate inferred ancestors of modern γ subunit genes.
