Different zeta globin gene deletions among black Americans.

Four types of chromosomes with a deletion between the human embryonic zeta and psi zeta 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 zeta globin gene [(X+) or (X-)]. The deletions are identifiable in Xba I digests of genomic DNA using an alpha or a zeta globin gene probe which yield fragments of 23 kb from (X+)-zeta alpha alpha chromosomes or 27 kb from (X-)-zeta alpha alpha chromosomes. Digestion with other enzymes and probing with both alpha and zeta probes gave fragments typical of the two zeta globin gene deletions previously identified in Polynesians. Among Black Americans, these zeta globin gene deletions have been found in combination with alpha globin gene deletions in trans but not in cis. Homozygotes have not been found. Hematologic data on carriers of the zeta globin gene deletions in association with Hb AS, SS, and SC suggest that these deletions have no effect on the function of the adult alpha globin genes.