Characterization of a new alpha zero thalassaemia defect in the South African population.

A new alpha thalassemia defect has been detected in the South African population. Restriction mapping of the alpha globin gene cluster in affected individuals has established that the defect is associated with the removal of 22.8-23.7 kb of DNA, including the psi zeta 1, psi alpha 1, psi alpha 2, alpha 2 and alpha 1 globin genes. The 5' endpoint of the deletion has been localized between the zeta 2 and psi zeta 1 globin genes, and the 3' endpoint lies 4-5 kb 3' to the alpha 1 globin gene. We have called the deletion - -SA in order to distinguish it from alpha zero thalassaemia defects described in other populations.