Mappings between the human and mouse imprinted loci. For human and mouse we take all the sequences of the mature miRNAs belonging to the imprinted loci on chromosomes 14 and 12 that are present in Rfam6.0, in our set of confirmed predictions (Additional files 4 and 5) and in the false negatives set (Additional files 7 and 8). We sort them according to their genomic coordinates and display on the graph the sequence similarity (i.e. the number of matches in a CLUSTALW alignment) for all possible pairs between the two set. Although a clear diagonal signal indicating cross-species conservation is visible, it is also very clear that species-specific features altering it are numerous, as described in the text.