PCR amplification of the genomic BCR-ABL1 rearrangements from twins. (A) Genomic BCR-ABL1 rearrangements from twins 1A and 1B at diagnosis; lanes: 1, marker; 2, diagnosis twin 1A; 3, diagnosis twin 1B; 4 and 5, negative controls; 6, no DNA control. (B) Genomic BCR-ABL1 rearrangements from twin 2A at diagnosis and relapse; lanes: 1, marker; 2, diagnosis twin 2A; 3, relapse twin 2A; 4, no DNA control. (C) Genomic BCR-ABL1 rearrangements from twin 2A and healthy twin 2B (Guthrie specimens); lanes: 1, marker; 2, Guthrie card DNA twin 2A; 3, Guthrie card DNA twin 2B; 4, no DNA control.