Evaluation of X-inactivation patterns in 4 obligate carriers of XLTT.

DNA digested with RsaI (lanes marked −) or RsaIand HpaII (lanes marked +) was PCR amplified using primers for HUMARA. Only alleles on inactive X chromosomes are amplified followingHpaII digestion. The allele carried by affected males is denoted A (data not shown). HUMARA lies just distal to the minimal region containing XLTT, and there were no recombinations between XLTT and HUMARA in individuals III-3, III-5, or IV-3. Although carriers IV-8 and V-1 were not included in the linkage analysis, they each must have inherited the X chromosome from their affected fathers, without any further recombinations.