Amplification of 2.45 kb product of MLL-AF4 rearrangement from RS4;11 cell line DNA and RS4;11 “imitation” Guthrie specimens by PCR. Lanes: M, DNA marker II; 1, no DNA control; 2, 100 ng positive control RS4;11 DNA; 3, 100 ng human placenta negative control DNA; 4, 100 ng normal genomic negative control DNA; 5–9, 10−1 through 10−5 dilutions of RS4;11 cells on imitation Guthrie specimens.