X-inactivation patterns with the HUMARA assay and BCR/ABL mRNA expression in MNC, CD34⁺HLA-DR⁺, and CD34⁺HLA-DR⁻ progenitors in steady-state marrow in AP CML. Results are shown for marrow from UPN 9. HUMARA PCR and BCR/ABL and β-actin RT-PCR reactions were performed as described in Materials and Methods. HUMARA was performed without (−) and with (+) predigestion with the methylation-sensitive endonucleasesHpaII and Cfo I. All samples show monoclonality. BCR/ABL results are shown after hybridization with the B3A2 probe. The housekeeping gene β-actin was used as a control for the presence of mRNA.