Hb Bart's level in cord blood and deletions of a-globin genes

Abstract

The white blood cell DNA of 36 cord blood samples with Hb Bart's in the red blood cells was studied for a-globin gene deletions by hybridization of DNA fragments digested by the restriction endonucleases Eco RI, Hpa I, Bam HI, and Bgl II. All 16 DNA samples from cord blood with Hb Bart's below 3% and no other abnormal hemoglobin had one globin gene deletion (athal2), except one which had two a-globin gene deletions (athal1). Most of the athal2 were of the rightward deletion athal2 genotype. Two new types of athal2 variation were found, probably due to a polymorphism somewhere in an area outside the a-globin gene. All 14 cases with Hb Bart's between 3.5% and 8.5% and no other abnormal hemoglobin had two a-globin gene deletions (athal1), except one that did not have any a-globin gene deletion and one that had one a-globin gene deletion. Three DNA samples of cord blood with Hb Bart's accompanied by Hb CoSp did not have any a-globin gene deletion. Sixty-five DNA samples from cord blood without Hb Bart's or other abnormal hemoglobin had no a-globin gene deletions, except one that had one a-globin gene deletion (athal2). Two of the 65 DNA samples were found to have triplicated a-globin gene loci.