Figure 4.

Deletions that cause α⁺-thalassaemia. The homologous duplication units X, Y and Z in which the α-genes are embedded are indicated as colored boxes. A cross-over between the mis-paired Z boxes during meiosis gives rise to the -α^3.7 and ααα^{anti 3.7} chromosomes. Cross-over between misaligned X-boxes give rise to -α^4.2 and ααα^{anti 4.2}.