Fusion genes resulting from unequal crossing-over at the β-globin gene cluster. Genes within the β-globin gene cluster are shown. Fusion genes arising from unequal crossing-over between the β and δ-globin genes (Hb Lepore/anti-Lepore) and the Aγ and β genes (Hb Kenya/anti-Kenya) are shown in A andB. (A) The generation of Hb Lepore and Hb anti-Lepore: The different types of Hb anti-Lepore fusion alleles that have been described include Hb Miyada and P-Congo, where the crossover regions occur between residues β12 and δ22 and between residues β22 and δ87, respectively. The different types of Hb Lepore alleles that have been described are Hb Lepore Hollandia, Baltimore, and Boston, where the crossover regions occur between residues δ22 and β50, residues δ50 and β87, and residues δ87 and β116, respectively. (B) The generation of Hb Kenya and Hb anti-Kenya: For Hb Kenya, the crossover region is between residues γ81 and β86. No Hb anti-Kenya variants have been described.
