Figure 1
From: Divergence of imprinted genes during mammalian evolution
Different patterns of divergence for imprinted and biallelically expressed genes. Imprinted genes (black) supposedly evolved faster than biallelically expressed genes (gray) in the common ancestors of rodents. After the split of rat and mouse (dots), imprinted genes seem to have been subject to stricter purifying selection than biallelically expressed genes. The present conservation pattern reflects a high divergence of imprinted human-rodent orthologs as opposed to high conservation between mouse and rat.