Physical mapping¹ of immunoglobulin loci <i>IGH@</i>, <i>IGK@</i>, and <i>IGL@</i> in the opossum <i>(Monodelphis domestica)</i>

Comparisons between marsupial and eutherian chromosomes provide valuable insight into the evolution of the mammalian genome (O’Brien et al., 1999). The grey short-tailed opossum (Monodelphis domestica) is the fi rst marsupial to have its genome completely sequenced. Unfortunately very few opossum genes have yet been physically mapped. Here we report the chromosome location of important marker genes. The adaptive immune system of vertebrates has evolved to recognize and respond to an exceptionally diverse range of antigens. Immunoglobulins (Ig) act as one of these mediators of antigen recognition. Ig molecules are comprised of two identical heavy chains in association with two identical light chains, each possessing variable and constant regions. In marsupials, as for eutherian mammals, Ig heavy chains are encoded by a single locus (IGH@) in the genome, and two light chain isotypes, Ig and Ig , are encoded at separate unlinked