IX. GENETICS AND HUMAN HEMOGLOBIN CHEMISTRY 



437 



B. FORMAL GENETICS OF THE Hb-A VARIANTS 



jMcndelian inheritance of the abnormal hemoglobin genes has been 

 shown for most of the Hb-A variants (Neel, 1956). The most pertinent 

 information on the inheritance of the hemoglobin genes is obtained from 

 marriages where one partner possesses two abnormal hemoglobins and 

 the other none (Rucknagel and Neel, 1961). Ranney (1954) described 

 marriages in which both Hb-C and Hb-S were observed in one partner; 

 only children with either Hb-S or Hb-C were found among the offspring 

 of these marriages. The allelism of the Hb-C and Hb-S genes was con- 

 firmed a few years later by the chemical investigation of Hunt and 

 Ingram (1958b); the same amino acid residue was found to be substi- 

 tuted in these two abnormal hemoglobins. 



One marriage supporting allelism of the Hb-E and Hb-S genes has 

 been described by Aksoy and Lehmann (1957). Veiy few marriages 

 involving a partner with two chemically characterized abnormal hemo- 

 globins have been reported. No individuals having two hemoglobins 

 abnormal in the a chain have thus far been reported. 



The low frequency with which the hemoglobins abnormal in the a 

 chain are observed in populations suggests very small probability that 



/ \ 



.y 



^^p" 



IL. 



\. y 





0-5 





Not examined 



Fig. 8. Family tree of the propositus (indicated by the arrow) with four hemo- 

 globins. (From Atwater et al, 1960a). The genotype of the individuals examined is 

 illustrated. The capital letters designate the hemoglobin types observed in the 

 corresponding individuals. The projiositus and one sister are doubly heterozygous. 



