Size fractionation of digested DNA by affinity beads. A. Counts of restriction fragments by size after in silico digestion of the Oryza sativa Os6.1 genome with NlaIII. The Y-axis of the graph displays the count per 25 bp bins. The graph top axis displays the total count for in silico slices of 100 bp. The graph demonstrates how a size fraction from 100 to 200 bp would contain more than ten times the number of fragments found in the 600 to 700 bp fraction. B. Fractionation strategies with SPRI magnetic beads. On the left, a bottom-delimited size fraction of the digested input DNA can be taken in a single step (thicker arrows path), or a sliced size fraction in two steps (thinner arrows path). Slicing is demonstrated in a digital electrophoretogram on the right. In practice, bottom delimiting in a single step is the most practical solution since the larger size fragments contribute relatively less to the final library.