A silent deletion in the beta-globin gene cluster.

A survey of the gamma-globin gene region of over 1000 normal individuals revealed a novel 2.5 kb deletion which removes the 5' end of the A gamma-globin gene. Unusually, this deletion in the beta-globin gene cluster is not associated with increased fetal haemoglobin production. Sequence analysis of the deletion endpoints revealed no significant homology at the breakpoint and failed to support a role for a proposed recombination hotspot in IVS-2 in the generation of this illegitimate recombination event. The existence of small "silent" deletions in the beta-globin gene cluster emphasizes the importance of deletion size in altering expression of the fetal globin genes.