Marsupials diverged from a common ancestor with placental mammals (which includes humans) approximately 180 million years ago. As an emerging model organism for metatherian mammals, Monodelphis domestica was selected for genome sequencing. Studies in this species will help identify functional genome features common to all mammals, and will also help to pinpoint differences, particularly those determining the different types of reproduction in placental versus non-placental mammals.
The Monodelphis genome project, based at the Broad Institute, has produced a high-quality draft sequence of a female South American opossum, the first marsupial species to be sequenced. In addition, the project has generated a large collection of single-nucleotide polymorphisms (SNPs) differing among several research populations of M. domestica, which will allow the mapping of genetic traits in these populations. Illumina-based RNA-seq to improve the opossum annotation is currently underway.