Family inheritance of the amorph Rh_null gene. (A) The genomic region encompassing exon 7 of RhCE gene was amplified by 2 pairs of primers In-6s/Ex-7a and In-6s/In-7a (Table 1). The In-6s/Ex-7a fragments were cut by BamHI (G↓GATCC), which is diagnostic of the mutation, and separated by native 6% PAGE. Although no cleavage is seen in control lanes, the respective fragments of 264 bp (denoted by a star) were cut completely in the Rh_nullpatient and partially in the heterozygotes. (B) Sequencing of the genomic fragments In-6s/In-7a. The 2 patients showed the same mutation, 2 deleted nucleotides (966T and 968A, boxed), in this fragment, which was sequenced on both strands. Intronic nucleotides are denoted by lowercase letters and exonic ones by uppercase letters. Dashes indicate identical nucleotides. The 2 primers for PCR amplification are overlined.