Comparative mapping of bidirectional promoters across species at orthologous positions. The reference set of bidirectional promoters is from 2,738 individual human protein coding genes (regulated by 1,369 bidirectional promoters). These regions were mapped to the species shown on the right of the panel. The orthology assignments were validated using ResSeq annotations in the non-human species, except for Cow_Comprehensive, which contained RefSeq, EST and OGS v1 annotations from cow. The heatmap is clustered keeping the vertical columns intact across all datasets to retain the relevance to the reference position in human. The order of the reference human gene set is dependent on the outcome of the clustering algorithm. The scale of the heat map is depicted as the number of human gene pairs used for predictions. Vertical bars representing each bidirectional promoter are colored purple when validated as orthologous in other species, royal blue when only one of the two flanking genes is annotated in cow, light blue when neither gene is annotated in cow, or off-white when no orthology is present for the human region.