The DNA deletion in an Indian δβ‐thalassaemia begins one kilobase from the Aγ globin gene and ends in an LI repetitive sequence

Abstract

High fetal haemoglobin levels of 5–15% are present in adult heterozygotes for δβ-thalassaemia as the result of large deletions of DNA. We have cloned DNA spanning the deletion breakpoint for a new Indian δβ-thalassaemia associated with mild anaemia. The 5’ breakpoint is at 42151 of GenBank file HUMHBB, which is about 1 kb 3’ of the ^Aγ globin gene poly A site at 41003. On the 3’ side of the breakpoint, the sequence is homologous to LI (KpnI) repetitive DNA located 3.6–10 kb 3’ of the β-globin gene: Indian δβ-thalassaemia DNA is 74% homologous to the inverted complement of HUMHBB from 69849 to 70020, followed by a region 78% homologous to the direct sequence of HUMHBB from 70534 to 71010. The precise location of the 3’ endpoint of this deletion has not been determined, but it is within LI sequences located more than 10 kb 3’ of the β-globin gene.