Analysis of ADA cDNA and genomic DNA of patient no. 2 and family. (A) Pedigree of family 2. Arrow indicates patient no. 2 (II-3); † indicates the deceased proband (III-1), an infant with SCID whose genotype is presumed. (B) Sequence of genomic exon 7 DNA (patient no. 2, left; control, right). Patient no. 2 is heterozygous for the A215T mutation. (C) Ethidium-stained agarose gel illustrating the method of screening cDNA clones for the R101Q mutation and for retention of exon 7 (see the Materials and Methods). Numbers at right indicate length in nucleotides of DNA markers. Lanes 1 and 2, PCR fragments (exons 1 to 8) digested with Bsg I. Lane 1, clone bearing R101Q mutation (cuts with Bsg I); lane 2, clone with wild-type (R101) exon 4 (lacks Bsg I site). Lanes 3 and 4, PCR fragments (exons 5 to 11) digested with Nci I. Lane 3, clone containing exon 7 (cuts with Nci I within exon 7); lane 4, clone with a deletion of exon 7 (lacks exon 7 Nci I site).