FIGURE 9.2 - A test restriction digest of DNA from cassava (Manihot duleis). Lanes 1 and 10 contain the PFGE lambda ladder. Lanes 2-9 contain DNA samples digested with increasingly higher concentrations of restriction enzyme. The conditions used in this test digest differ from those described in CHAPTER 9, however the principle of determining optimal digestion conditions from the gel remains the same (see FIGURE 9.1). A light blue, dotted rectangle has been added to show the optimal fragment size range. In lane 2 the majority of the DNA is > 350 kb, and in lane 5 the majority of the DNA is < 100 kb. However, lanes 3 and 4 appear to contain numerous fragments in the optimal size range. The reaction conditions used in either lane 3 or 4 (or conditions intermediate between the two) should be used in a large-scale restriction digest (see CHAPTER 10).