(A) By using different pairs of RH D specific primers and nested RT-PCR to amplify the RH Del gene, there was a deletion of exon 9 of RH Del gene (a). The results were further confirmed by direct sequencing of the nested RT-PCR product (b) and (c). The sequences of primers P1, P2, P3 and P4 are shown in the text. (B) The breakpoint region sequence of Del in comparison with D, Ce, and ce alleles.