Analysis of avian deletion block sizes on lizard and human chromosomes. (A) Frequency distributions of missing blocks arranged by size reveal deletion block sizes are significantly larger on average in lizard (black bars) than human (white bars; Pair-wise Wilcoxon Signed Ranks test). The sizes of each blocks corresponds to the minimal size of the human and lizard chromosomal segments containing all the orthologs within each of the avian missing syntenic blocks. (B) Cumulative sum of avian deletion block sizes in lizard (black) and human (white). Only blocks of three or more genes presented on Additional file 1: Table S1A are included in the analysis. Abbreviations: bp, base pairs.