Sequence motif analysis. All possible fragments of length 2-5 were enumerated and their observed and expected frequencies were computed. The x-axis represents the natural log of the ratio of the observed to the expected frequency. The y-axis is the histogram of these values in 6 different sets: Immune IDDs, non-immune IDDs, ordered domains, random immune IDDs, random non-immune IDDs, and random ordered domains. Panels A-D illustrate motifs of length 2-5, respectively. Random sequences produced zero counts for the motifs of length 5.