(A) Description of the BACs (grey lines) used for sequencing the snake HoxD cluster and the surrounding regulatory gene deserts. The scheme reflects the relative genomic distances between genes (black boxes). (B) Comparison between the sizes of the HoxD cluster (left), the 5’-located gene desert (centromeric in the mouse) and the 3’-located gene desert (telomeric in the mouse) relative to genome size. The species used are mouse, human, cow, dog, horse, opossum, chicken, zebra finch, lizard, corn snake, cobra, python, frog, zebrafish, stickleback and medaka. Snakes are shown in red and lizard in green, whereas other vertebrates are in blue. The linear regression line and 95% confidence band were calculated excluding the snakes and lizard data. (C) Graphs representing the repeat content in the snake and mouse HoxD clusters as well as within the flanking gene deserts. The various types of repeats are shown on the right with a colour code.