RT-PCR amplification of AML1 with allele-specific primers. Platelet cDNA was amplified in 2 tubes with an R primer complementary to either the WT (in the first tube) or the M (in the second) AML1 allele and a common F primer yielding a 484-base pair (bp) product, which was analyzed by ethidium bromide-stained 2% agarose gel electrophoresis. (A) Representative RT-PCR analysis. Both WT and M transcripts are expressed in patients while only the normal allele is detected in the control. A 100-bp DNA ladder is shown on the left lane. (B) Comparison of WT and M mRNA levels. Expression of M relative to WT mRNA, set as 100%, is indicated by the bars. Results represent the average of 2 PCR assays performed using serial cDNA dilutions.