Heterozygosity for the 836G and 836A Rh50 alleles in Rh_null(YT). The genomic region encompassing exon 6 of the Rh50 gene was amplified by two pairs of primers In-5s/Ex-6a and In-5s/In-6a (Table 1). (A) 1.8% agarose gel electrophoresis of the amplified In-5s/Ex-6a (246 bp) and In-5s/In-6a (380 bp) fragments. Lanes are designated as in Fig 1. (B) SSCP analysis of the In-5s/Ex-6a fragments followed by silver staining. The shifted band seen in Rh_null(YT) (lane 3, arrow-indicated) is the single-stranded form containing 836A. (C) Sequencing profiles of the subcloned In-5s/In-6a inserts derived from Rh_null(YT). The presence of both GGA and GAA codons (denoted by two arrows) confirmed the proband to be heterozygous for the missense mutation.