Schematic representation of the method used to identify syntenic regions between two species. In this figure, the pseudogenes are depicted as yellow boxes and human genes that have orthologs in mouse have been labeled. As explained in the text, the human gene SPRY1 and Y1223_HUMAN sandwich the processed RP pseudogene of RPL21 and have corresponding orthologs in the mouse genome. Thus, we identify this region as being syntenic between human and mouse. Orthologs were identified based on annotations from Ensembl release 36.