Abstract
A mutant EcoRI endonuclease restriction site was identified in 3 of 37 black subjects and in 2 sibs of 1 of these persons. This mutation was not encountered in 13 whites. It is located approximately 6 kilobases inside the normal site in the 5'' flanking sequence of the .alpha.-globin chain complex. The shortened .alpha.-globin gene-bearing segment produced in the EcoRI digest produces a restriction map similar to that observed for the common .alpha.-globin gene deletion observed in the black population. The restriction map with BamHI is normal, confirming that all 4 .alpha. loci are present.