RT-PCR analysis of ETV6/JAK2 fusion products. Total RNA from the ALL case (lane 1), the CML case (lane 2), and normal WBCs (lane 3) was used in a RT-PCR with primers located in the relevant exons of ETV6 and JAK2 (see Materials and Methods section). In each case a major product is observed, together with a minor product of a larger size. The different PCR products are the result of alternative splicing events as shown in Fig 3. Marker size is indicated to the left.