CYP7A1 mutation detection. (a) TaqI digested full-length CYP7A1 cDNA produced by RT-PCR from control and patient (IV-17) RNA showing homozygosity for the additional TaqI site. (b) Screening of the immediate family of the proband. Homozygotes are represented by filled squares and circles and heterozygotes by half-filled squares and circles. The coding region of exon 6 was amplified by PCR and digested with TaqI. (The double horizontal lines indicate a consanguineous mating.) (c) Pedigree of family with CYP7A1 deficiency. Individuals II-1, II-4, III-3, III-5, III-6, and IV-11 are depicted as obligate carriers. *It cannot be inferred which one of these two subjects was the initial carrier.