IX. GENETICS AND HUMAN HEMOGLOBIN CHEMISTRY 441 



more direct and striking demonstration of the exchange of subunits upon 

 recombination. Itano and Robinson (1959) recombined a mixture of 

 Hb-I <«,'i8o^) and of Hb-S (a-^ ^J") and observed the formation of two 

 new hemoglobins, one with the electrophoretic iriobility of Hb-A iay'' fS-y'') 

 and the other, electroi^horetically faster than Hb-A, resulting from 

 the combination of a/ dimers with f^-/ dimers. Observing the presence of 

 four hemoglobins after recombination of two hemoglobins having differ- 

 ent jieptide chains, Itano and Robinson (1959) predicted that in indi- 

 viduals doubly heterozygous for two abnormal hemoglobins, a similar 

 situation could be found. Their prediction was scon to be validated by 

 the discovery of individuals with four hemoglobins (Atwater et al., 

 1960a; Raper et a/., 1960). 



Jones et al. (1959a) have used dissociation at alkaline pH and 

 recombination, to determine the gross chemical structure of Hb-H (see 

 Section IV,H,1). Recombination of Hb-H with Hb-S^" (a-^* fS-^*) re- 

 sulted in the formation of four components, which were identified as fi^^, 

 I3i^*, ao"* ^2-'^, and ay"* /So^*, thus showing that Hb-H is an abnormal 

 hemoglobin made up of fS'^ chains only. 



Jones et al. (1959b) have shown that «2'''* subunits can be transferred 

 from Hb-S«" (ao^* ^2^"") to Hb-F and that ao subunits from Hb-F could 

 associate with ySo^ dimers produced by dissociation of Hb-H to give Hb-A 

 (a2^ ^o^) ; this indicates that the a-2 dimers of Hb-A and Hb-F can be 

 exchanged and are probably identical. Weatherall and Boyer (1962) 

 have reported the formation of Hb-A and hemoglobin F/G (a-,^ y/) upon 

 acid recombination of Hb-F (a^'" yo^) and of Hb-G (ao^/S.-M. 



The results of the recombination experiments have suggested (Itano 

 and Robinson, 1959) a method for identifying the altered peptide chain 

 of any electrophoretically abnormal hemoglobin. A hemoglolnn in which 

 the abnormal chain has been identified is recombined with an abnormal 

 hemoglobin in which the abnormal chain is unknown. If the two hemo- 

 globins are abnormal in different peptide chains, namely, if one has 

 abnormal a chains and the other abnormal /? chains, new hemoglobin 

 species, which are electrophoretically different will be produced upon 

 recombination. If the two hemoglobins are abnormal in the same chain, 

 no new hemoglobin species will be produced upon dissociation and recom- 

 bination. A microscale method of analysis has been devised by Gammack 

 et al. (1960) to determine by dissociation and recombination the altered 

 peptide chain of an abnormal hemoglobin. By this method of analysis 

 Gammack et al. (1961) were able to individuate the abnormal peptide 

 chain of several abnormal hemoglobins. The dissociation and recom- 

 bination analysis has also been applied to the study of other human 

 hemoglobins and of animal hemoglobins. 



