Different ζ globin gene deletions among Black Americans

Abstract

Four types of chromosomes with a deletion between the human embryonic ζ and ψζ globin genes were identified among 2.8% of 321 Black Americans from Georgia. Two deletions of approximately 11 kb which differed by about 300 bp occurred on chromosomes with or without a polymorphic Xba I site 5′ to the ζ globin gene [(X+) or (X-)]. The deletions are identifiable in Xba I digests of genomic DNA using an α or a ζ globin gene probe which yield fragments of 23 kb from (X+)-ζ*αα chromosomes or 27 kb from (X-)-ζ*αα chromosomes. Digestion with other enzymes and probing with both α and ζ probes gave fragments typical of the two ζ globin gene deletions previously identified in Polynesians. Among Black Americans, these ζ globin gene deletions have been found in combination with α globin gene deletions in trans but not in cis. Homozygotes have not been found. Hematologic data on carriers of the ζ globin gene deletions in association with Hb AS, SS, and SC suggest that these deletions have no effect on the function of the adult α globin genes.