The Chesapeake Bay Retriever is a large-sized breed of dog belonging to the Retriever, Gundog, and Sporting breed groups. The American Chesapeake Club includes a discussion on color: A white spot on the breast (not extending above the sternum), belly, toes or back of the feet is permissible, but the smaller the spot the better. The American Chesapeake Club includes a discussion on color: A white spot on the breast (not extending above the sternum), belly, toes or back of the feet is permissible, but the smaller the spot the better. White beyond these areas and black anywhere on the body is not allowed in the breed standard. 'Linkage analysis and comparative mapping of canine progressive rod–cone degeneration (prcd) establishes potential locus homology with retinitis pigmentosa (RP17) in humans'.