The opossum joins the growing list of animals that have had their genomes sequenced. The folks at the Broad Institute led an international team reporting today in Nature that the grey, short-tailed opossum (often used as a model for spinal cord injury and other disorders/diseases) has about the same number of genes as humans do.

What’s more interesting and surprising is that most of the sequence differences found in the opossum genome, compared with other mammals, are in noncoding regions thought to regulate gene activity, suggesting that evolution was driven not by having different genes, but by different ways of regulating the same genes._ The researchers also say that these sequences changes came from transposons, or “jumping genes.”