Figure 1.

Schematic diagram showing blocks, words and the greedy algorithm for finding significant blocks. Arrow corresponds to a k-mer word, and its direction indicates direct or reverse strand. Circle indicates presence of the word shown on the left within the block shown on top. Big circles are used to discriminate true hits from background noise indicated by small circles. Three blocks (numbers 10–12) containing three or more hits are considered to be significant and indicated by yellow color.