Southern blot analysis showing the inheritance of a deletion at the 3′ end of the DKC1 gene. (A) Hybridization of a DKC1 probe 31g1K17 (cDNA nucleotides 744-1565) to Taq I digests of genomic DNA from the following family members: lane 1, mother of patient HO (I-1); lane 2, sister of patient HO (II-1); lane 3, patient HO (II-7); lane 4, niece of patient HO (III-1); and lane 5, nephew of patient HO (III-2). Numbers in brackets refer to the pedigree in Fig 5. Note that the 1.6-kb fragment produced by the deletion is not detected in the mother. (B) Hybridization of an MPP1 probe 39g1B21 (cDNA nucleotides 1117-1822) to Taq I digests of genomic DNA from the following: lane 1, patient HO; and lane 2, a normal control. Note that both probes hybridize to fragments of the same size. Two fragments of coincidental size are seen in the normal sample, 1 of which is deleted in patient HO.