Orthology (one-to-one) of overlapping gene pairs between A. aegypti and A. gambiae. Genes have been color coded to represent orthologous relationships between the two species: red color represents A. aegypti and blue color represents A. gambiae. The one-to-one orthologous gene pairs that are localized in positionally overlapping manner in both the genomes are indicated by green color. The number of gene pairs is shown for each group. The circles A and C represent the young-young gene pairs, circles B and D represents the old-old gene pairs, and the gene pairs outside the circles represent young-old gene pairs in each species. The 2x2 contingency tests based on the count statistics of young-young and old-old genes between A. aegypti and A. gambiae (i.e. the A, B, C and D gene groups) shows that there is a significant bias in the distribution of these genes between the two species (shown as the column graph in the middle). In this graph, the y-axis shows the number of gene pairs corresponding to the four gene groups; and the gene groups are represented by the x-axis. The columns are color coded same manner as that of the gene groups (A, B, C and D).