SegB endonuclease cleaves DNA at sites that have different susceptibility for the enzyme cleavage. Lanes T2La, T4 and T2Lb contain products of SegB endonuclease cleavage reactions that used a phage T2L fragment, amplified with primers #1 and #2, a phage T4 fragment, amplified with the same primers, and a phage T2L fragment amplified with primers #1 and #5, respectively, as substrates. Locations of the primers #1, #2 and #5 are shown in Figure 1. The cleavage reactions were carried out under the standard conditions, but the amount of SegB endonuclease varied as indicated. Lanes M contain HyperLadder I DNA markers (Bioline). The arrowheads show positions of the 1.24 kb and 0.71 kb, and 0.59 kb and 0.46 kb SegB products cleaved in the sites of T2L tRNAAsn gene (lanes 5 and 8) and of T2L tRNASer gene (lanes 7 and 10), respectively.