RT-PCR analysis of allelic expression of the P55 gene. RNA of heterozygous patients was submitted to RT-PCR. Amplified products were digested with Hha I and analyzed by gel electrophoresis and ethidium bromide staining. (A) Illustrates the results obtained from a patient with monoclonal hematopoiesis in platelets and granulocytes; (B) patient with monoclonal hematopoiesis only in platelets; (C) patient with polyclonal hematopoiesis; (D) patient with a nonrandom X-chromosome inactivation pattern. U, undigested PCR products; 1, platelets; 2, T lymphocytes; 3, granulocytes. Arrows indicate the size of the fragments in base pairs.