Different hematologic phenotypes are associated with the leftward (-alpha 4.2) and rightward (-alpha 3.7) alpha+-thalassemia deletions.
We have compared the phenotypes of the two common deletion forms of alpha+-thalassemia by analysis of umbilical cord blood samples from Melanesia. Homozygotes for the leftward, 4.2-kilobase, deletion (-alpha 4.2) had significantly higher levels of Hb Bart's at birth than homozygotes for the rightward, 3.7-kilobase, deletion (-alpha 3.7). Compound heterozygotes for each deletion had intermediate values. Although deletion forms of alpha 0 thalassemia were not found in this survey, nondeletion alpha-thalassemia was present at low frequency. Since the predominant rightward deletion in this population, -alpha 3.7III, entirely removes the alpha 1-gene and the 4.2-kilobase deletion deletes the alpha 2-gene, these data indicate that the alpha 2-globin gene has a higher output than the alpha 1-gene, on single alpha-gene chromosomes.
D002872:Chromosome Deletion; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics; D006455:Hemoglobins, Abnormal / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008542:Melanesia; D010641:Phenotype; D013789:Thalassemia / Q000097:blood / Q000235:genetics*
D006455:Hemoglobins, Abnormal; D005914:Globins; C030448:hemoglobin Bart's