Long-range amplification on digested and nondigested DNA. (A) The first three steps were performed using a PCR-based technique after adaptor ligation to digested DNA, with an adaptor primer and anALK gene-specific primer, to determine the chromosome 1 gene involved in the (1;2) translocation. By walking on the chromosome from the ALK gene across the breakpoint to this unknown gene, we demonstrated that this chromosomal rearrangement fused the ALKgene on chromosome 2p23 to the TPM3 gene on chromosome 1q25. The 1.6-kb Ssp I fragment was only partially sequenced to yield the first 170 bp of this fragment at the 5′ end, allowing preparation of primers for the next step. This 170-bp sequence showed a complete identity to the sequence of intron 7 of the TPM3 gene. (B) The next three PCR steps were performed on undigested DNA and confirmed that all PCR fragments previously generated were colinear. The longer 2.2-kb PCR fragment obtained on undigested DNA was entirely sequenced and showed 99.9% identity with a 1,146-bp sequence in part of intron 7 of the TPM3 gene deposited in the GenBank database25 (accession no. X79910).