Deletions in the α-globin gene cluster. The α-globin gene cluster is located on the short arm of chromosome 16 near the telomere. The three active globin genes, ζ2, α2, and α1, are represented by red boxes, whereas the four pseudogenes are represented by open boxes. The extent of the deletions are shown by the solid blue lines. The (--^HW) deletion encompasses more than 300 kb, and is represented with arrows in the figure.26 The −(α)^20.5 deletion spares the ζ2 gene, and removes the α2 gene and the 5′ region of the α1 gene.29