A recent duplication of <i>Adam9</i> through retroposition.

<p>Locations of <i>Adams 9a</i> and <i>9b</i> in the opossum genome, as well as the gene structure of <i>Adam9b</i>, are shown. Structure of the <i>Adam9a</i> mRNA is also shown for comparison, with black vertical lines representing splice sites (not to scale). The <i>Adam9b</i> pseudogene contains a polyA sequence, and the only intron was identified as an opossum retroposon (Mdo3LTR1a/ERV1), which was likely inserted after the original retroposition event that generated <i>Adam9b</i>. This insertion caused a frameshift.</p>