Cleavage of pseudo-Y structure at 50°C. Lanes: 1 to 3, size markers (10, 15, and 21 nt, respectively); 4, oligonucleotide FS (37 nt) with truncated sequences; 5, FS after incubation of FS plus FA with Taq DNA polymerase; 6, FS after incubation of FS plus FA with FEN; 7, FS after incubation of FS alone with Taq DNA polymerase.