Southern blot analysis of the jumping translocation. (A) BAL31 exonuclease treatment of normal genomic DNA. A longer incubation time with BAL31 exonuclease (indicated in minutes at the top of the lanes) reduces the signal of the terminal telomeric repeat and results in the appearance of the internal TTAGGG-fragments. (B) Southern blot analysis of DNAs from the JT patient and a normal individual using the telomeric repeat as a probe. The DNAs were digested with BAL31 exonuclease, followed by the Hinf I restriction. Arrows indicate the JT-specific fragments (4.4 kb and 5.5 kb). (C) Southern blot analysis of DNAs from the patient and a normal individual using the nontelomeric probe A (see Fig 3a). The DNAs were digested withEcoT14 I. Arrows indicate the JT-specific fragments (6.0 kb and 7.0 kb). The arrowhead indicates the fragment derived from the normal allele (2 kb).