The form of hereditary persistence of fetal haemoglobin (HPFH) that commonly occurs in black populations is an inherited disorder of haemoglobin synthesis characterized by a uniformly high level of fetal haemoglobin (HbF) synthesis in all the erythroid cells of affected adult individuals 1,2. The precise molecular basis of the HPFH phenotype remains unknown, but is of great interest because of the knowledge that could be gained, through its understanding, of the mechanisms that regulate the expression of globin genes during development. The most common form of HPFH in black populations is associated with an extensive deletion that includes the normal adult (δ and β) globin genes and adjacent flanking DNA3-8. To investigate this disorder in more detail, we have cloned the DNA encompassing the region of the gene deletion in a case of HPFH and have determined the nucleotide sequence across the 5′ end point of the deletion within the non-α-globin gene complex. We report here that this end point maps at the midpoint of a member of the 'AluI' family of repetitive sequences located approximately 4 kilobases (kb) to the 5′ side of the δ-globin gene. Such repetitive sequences may be 'hot spots' of recombination, and are possibly involved in regulating gene expression.
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