Rh Nomenclature
The Rh blood group system has two sets of nomenclatures: one developed by Ronald Fisher and R.R. Race, the other by Wiener. Both systems reflected alternative theories of inheritance. The Fisher-Race system, which is more commonly in use today, uses the CDE nomenclature. This system was based on the theory that a separate gene controls the product of each corresponding antigen (e.g., a "D gene" produces D antigen, and so on). However, the d gene was hypothetical, not actual.
The Wiener system used the Rh-Hr nomenclature. This system was based on the theory that there was one gene at a single locus on each chromosome, each contributing to production of multiple antigens. In this theory, a gene R1 is supposed to give rise to the “blood factors” Rh0, rh’, and hr” (corresponding to modern nomenclature of the D, C and e antigens) and the gene r to produce hr’ and hr” (corresponding to modern nomenclature of the c and e antigens).
Notations of the two theories are used interchangeably in blood banking (e.g., Rho(D) meaning RhD positive). Wiener's notation is more complex and cumbersome for routine use. Because it is simpler to explain, the Fisher-Race theory has become more widely used.
DNA testing has shown that both theories are partially correct. There are in fact two linked genes, the RHD gene which produces a single immune specificity (anti-D) and the RHCE gene with multiple specificities (anti-C, anti-c, anti-E, anti-e). Thus, Wiener's postulate that a gene could have multiple specificities (something many did not give credence to originally) has been proven correct. On the other hand, Wiener's theory that there is only one gene has proven incorrect, as has the Fischer-Race theory that there are three genes, rather than the 2. The CDE notation used in the Fisher-Race nomenclature is sometimes rearranged to DCE to more accurately represent the co-location of the C and E encoding on the RhCE gene, and to make interpretation easier.
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