Triplication of alpha-globin genes is responsible for unusual alpha 113Leu/alpha 113His-globin chain ratios in sheep.
By investigations at the DNA and protein level, it has been shown that in sheep a previously detected, presumed quantitative allele of the II alpha 113His gene, displaying a reduced efficiency (called the II alpha 113His decreases gene), is carried by a chromosome bearing three alpha-globin loci. In particular, five sheep having an alpha 113Leu/alpha 113His-chain ratio of about 13:1 (13:1 phenotype) possessed the -I alpha 113Leu-II alpha 113Leu-/-I alpha 113Leu-II alpha 113Leu-III alpha 113His decreases genotype. One sheep showing a alpha 113Leu/alpha 113His-chain ratio of about 3:1 (3:1 phenotype) had the -I alpha 113Leu-II alpha 113His-/-I alpha 113Leu-II alpha 113Leu-III alpha 113His decreases genotype, while one sheep having a chain ratio of about 6:1 (6:1 phenotype) carried the -I alpha 113Leu-II alpha 113Leu-II alpha 113His decreases-/-I alpha 113Leu-II alpha 113Leu-III alpha 113His decreases genotype. Nineteen sheep, displaying the common phenotypes, all possessed the alpha alpha/alpha alpha gene arrangement. Furthermore, the possible location of the gene with reduced efficiency and the expression of the three genes in the triple alpha-globin loci chromosome are discussed.
Istituto di Fisiologia Umana, Università Cattolica S. Cuore, Roma, Italy.
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Di Gregorio
D000818:Animals; D004247:DNA / Q000032:analysis; D005914:Globins / Q000235:genetics*; D006639:Histidine / Q000235:genetics; D007525:Isoelectric Focusing; D007930:Leucine / Q000235:genetics; D005810:Multigene Family; D010641:Phenotype; D011110:Polymorphism, Genetic; D012756:Sheep / Q000097:blood / Q000235:genetics*
D006639:Histidine; D005914:Globins; D004247:DNA; D007930:Leucine