Gene backgrounds of partial D phenotypes. D variant phenotypes that are proposed to arise through gene conversion or double cross-over events are shown. The hybrid genes are represented as 10 exons, of which some (black boxes) are derived from the RHD gene, and others (white boxes) from the RHCE gene. The D^IVa phenotype involves either point mutation or gene conversion within exons 3 and 7 of the RHD gene, and are thus depicted as small sections of RHCE exons.