Figure 6. .

Skewed X inactivation in females with an HCCS mutation. X-chromosome inactivation determined by amplification of an AR-sequence polymorphism and digestion of genomic DNA isolated from lymphocytes with HpaII (indicated with plus [+] and minus [−] signs, respectively). The ratio of the X-inactivation pattern is given below the respective pedigree symbol. All females carrying an HCCS mutation show nonrandom or extremely skewed X inactivation (patient MS1 in panel A; patient MS2 in panel B; and II.1, II.7, and their mother [I.1] in panel C). D, Part of the DNA sequence electropherogram of HCCS exon 6, obtained from an RT-PCR amplicon of patient MS1. Only the wild-type allele (c.589C) (arrow) is expressed in her lymphoblastoid cells.