Linked Genes 297 



is given by homozygous r, r^, R" , and R- individuals than by 

 those persons who have only one of these genes and also either 

 R' or R'^, the results expected from all the possible Rh genotypes 

 are listed in Table 14. The Hr factor can be used as a pre- 

 sumptive test for the homozygosity or heterozygosity of type 

 Rhi fathers in families with erythroblastic infants (Wiener, 

 1946). 



Other Alleles 



Two other alleles at the r locus have been discovered although 

 they are rare. Race and Taylor and Murray, Race, and Tay- 

 lor found genes which they designated Rhy and Rh^ and which 

 Wiener has designated R' " and R^ 2, both of which react posi- 

 tively with Rh' and Rh" antisera but negatively with anti-Hr 

 serum. Gene R^ " gives negative results and JRi 2 positive re- 

 sults with Rho antiserum. Although these genes appear to be 

 rare among whites, they are far more common among Mexican 

 Indians. 



Wiener has also found some bloods which give intermediate 

 reactions. He suggests that there may be some ''intermediate" 

 genes such as are listed in Table 16. 



Linked Genes 



Multiple alleles at one locus have not been the only explana- 

 tion offered for the inheritance of the Rh blood types. Fisher, 

 Race, Levine, and others have suggested an alternate explana- 

 tion. They assume that three loci are concerned, that these loci 

 are very close together on one chromosome, and that at least two 

 alleles are present at each locus. The pairs of genes are T> and 

 d, C and c, and E and e, and the antibodies with which they 

 react are A or anti-D, 6 or anti-d, F or anti-C, y or anti-c, H or 

 anti-£'^ and rj or anti-e. Comparing this terminology of Levine 

 and the British workers with that of Wiener previously dis- 

 cussed, we find that anti-C is the same as anti-Rh' and anti-c 

 the same as anti-Hr'. Similarly, anti-D is anti-Rho and anti-d 

 is anti-Hro, and anti-E is anti-Rh" and anti-e is anti-Hr". The 

 anti-Hr' serum was originally called St by Race and Taylor and 

 simply anti-Hr by Levine. 



The symbols D and d, C and c, and E and e are not intended 



