Clonality analysis of leukemic cells obtained from the initial APL phase (lane 1) and subsequently developed AML phase (lane 2) in patient 2.1-1 

RNA was reverse transcribed using random primers and cDNA were amplified with primers specific for the iduronate-2-sulfatase(IDS) gene as described.1-2 Amplified fragments were digested with the methylation-sensitive HpaII restriction endonuclease prior to agarose gel electrophoresis. Two differently sized bands of 133 and 158 bp are visible in lanes 1 and 2, which correspond to distinct allelic methylation patterns. M indicates molecular weight marker (ΦX 174 DNA/BsuRI).