Heterogeneity of the 7-Globin Gene Sequences in Japanese Individuals: Implication of Gene Conversion in Generation of

The linked fetal globin genes (the G/- and Az-globin genes) were cloned from Japanese individuals with three different haplotypes of the Hindlll polymorphisms within the y-globin genes. Determination of nacleotide sequences of the segment spanning from IVS2 to the 3 ' flanking region of each /-globin gene revealed that nucleotide differences are located at 43 positions and a stretch of simple GT or GC sequences. Almost half of the nucleotide changes could be accounted for by gene conversion between the Gy- and A7-globin genes. We found that gene conversion had created the Sad polymorphic site just downstream of the A7-globin coding region. Association of the Sad polymorphic site with the Hindlll polymorphic site suggests that the region containing these two sites was derived from that of the linked Gz-globin gene through a gene conversion event The nucleotide sequences obtained here are identical to those of the Caucasoid fetal globin genes of the same haplotypes, with the exception of some sequence changes in the hot spots of mutations. These results indicate that the sequence heterogeneity of the /-globin genes can be classified into three major categories according to Hindlll haplotypes. The possible mechanisms of generation of the heterogeneity of the 7-globin gene sequences are discussed