Model for antenatal diagnosis of β -thalassaemia and other monogenic disorders by molecular analysis of linked DNA polymorphisms

Polymorphisms of DNA restriction sites within the human fetal globin genes have been used to identify chromosomes that carry β-thalassaemia genes in individuals heterozygous for this disease. This has allowed an antenatal diagnosis for β-thalassaemia to be carried out by observation of the pattern of the inherited polymorphism of a linked DNA sequence not involved in the genetic pathogenesis of the disease. In the populations we have investigated there is no constant pattern of polymorphism that segregates with the β-thalassaemia gene. The use of linked polymorphisms should, therefore, be applicable to antenatal diagnosis both of β-thalassaemia and of any other single-gene defect for which there is a DNA probe specific for a sequence linked to the affected locus.