Stability test for maize B73 BIBAC clones in E. coli. BIBAC clones were randomly selected from the maize B73 BIBAC library that was constructed using the BIBAC-S vector. DNA samples were prepared from cultures grown for 16 h, 24 h, 48 h, 72 h and 96 h at 37°C (sub-cultured every 24 h), and were digested with I-Sce I and separated on CHEF gels (the samples were loaded in order for each clone). The six BIBAC clones shown (from left to right) are A1, B1, B6, C1, C2 and C3, which contain inserts of about 40 kb, 140 kb, 160 kb, 80 kb, 100 kb and 80 kb, respectively. The molecular weight marker is Midrange I (New England Biolabs).