298 



Blood Groups 



to imply any dominant-recessive relationship but indicate the 

 genes that are found at the same locus. Evidence from gene 

 frequencies makes it appear that the order of the genes on the 

 chromosome is D-C-E. 



Let us now compare the genotypes of the two theories. Ac- 

 cording to the theory of linked genes, genotype CDe reacts with 

 C, D, and e serum. It corresponds with gene R^ of the other 



TABLE 16 



Four Additional Alleles at the r Locus and Their Reactions with 



THE Standard Antisera 



(From Wiener in Science [1944]) 



theory, a gene which reacts with anti-Rho and anti-Rh', but not 

 with anti-Rh" (Table 14). Genotype cDE is the same as R^ 

 and reacts with anti-D (anti-Rho) , anti-E (anti-Rh") , and anti-c 

 (anti-Hr'). Genotype cDe is r^ and reacts with anti-D (anti- 

 Rho), anti-c, and anti-e (anti-Hr"). Similarly Cde is R', react- 

 ing with anti-C (anti-Rh') anti-d (anti-Hro), and anti-e, 

 and cdE is R'' and reacts with E (anti-Rh"), anti-d, and anti-c. 

 Genotype cde corresponds to r and reacts with anti-c, anti-d, 

 and anti-e sera. A third allele has been found at the C locus ; it 

 is called C"'. 



Both theories have their advocates and it is unnecessary now to 

 decide between them. They raise again the interesting problem 

 of multiple alleles versus closely linked genes, a problem which 

 was mentioned in Chapter 10. As long as genes C, D, and E are 

 completely linked, the question is largely an academic one. If 



