RT-PCR for primary acute leukemias, leukemia cell lines, and normal lymphocytes. Total cellular RNA was recovered from 9 of the sequenced primary acute leukemias in addition to RNA from 3 leukemia cell lines and normal lymphocytes. RT-PCR for p15 was performed to assess transcription in these samples. p15 expression was found to correlate with density of methylation and with the presence of completely unmethylated alleles in a population. KG1a, which does not express p15,6 has a nonspecific PCR product of a size not matching p15. The control GAPDH RT-PCR was done using low cycle number (20 cycles) and is shown below demonstrating that intact and relatively equal RNA was used for each sample. (+) Indicates the addition of MMLV RT enzyme; (−) indicates control RT reaction to which RT enzyme was not added. The size of p15 product is 450 bp and the size of GAPDH product is 306 bp.