Restriction map of germline ETV6 (GL ETV6), germline AML1 (GL AML), and the derivative 12 (DER 12) and derivative 21 (DER 21) alleles from patient 41. ETV6 exons are shown as solid boxes (▪). ETV6 is depicted as a straight line; AML1 is crosshatched (▧). The open boxed area (□) depicted at the breakpoint junction in the two derivative alleles represents a deletion of 540 bp of the ETV6 gene and 165 bp of the AML1 gene observed in this patient. Restriction enzyme sites are B, BamHI; G, BglII; R, EcoRI; S,SstI; M, MluI; H, HindIII; and Sc, ScaI .