Possible duplication of the hemoglobin alpha chain locus in sheep.

Only one type of alpha chain has been described so far in the hemoglobins of adult domestic sheep. A variant (Hb D) of the alpha chain, characterized by a substitution glycine leads to aspartic acid at position 15, has been described in Yugoslavian sheep. In this paper we report the identification of a second alpha chain (alpha 2), observed in several sheep when the globin was analyzed by CM-cellulose chromatography or the total hemolysate submitted to isoelectric focusing. The ratio of this chain to the usual one (alpha 1) in the globin of different animals is equal to either 1 : 2 or 1 : 4. The structural difference between alpha 1 and alpha 2 chains consists in the replacement of a leucine residue by an histidine in the position 113 or 114 of the polypeptide chain. Preliminary data on the frequency of the alpha 2 chain in eight domestic breeds indicate that this chain is fairly common, being present in 15 out of 40 animals examined. The results of breeding experiments between sheep of an appropriate alpha chain phenotype suggest the possibility of a duplication of the hemoglobin alpha locus in the Ovinae.