The delta-beta-crossing-over site in the fusion gene of the Lepore-Boston disease might be localized in a preferential recombination region.

The delta-beta-fusion gene of heterozygous Lepore-Boston patient contains a large intervening sequence (IVS2) which could derive entirely from the beta-gene. This conclusion was obtained using a specific beta-IVS2 probe to analyse the physical map of the Lepore-Boston DNA which has shown the presence of a specific beta-AvaII site at the 5' end of the delta-beta-Lepore fusion gene. Thus, the crossing-over between delta- and beta-globin genes to explain the delta-beta-Lepore recombination could be localized between the delta-codon 87 and the 5' end of the beta-IVS2. The second protein-encoding region might represent a preferential recombination position in disorders associated with structurally abnormal globin chains resulting from fusion genes.