Meiotic recombination in the β globin gene cluster causing an error in prenatal diagnosis of β thalassaemia

Abstract

In the course of a prenatal diagnosis for β thalassaemia by linkage analysis of restriction fragment length polymorphisms, a homozygous β thalassaemia fetus was misdiagnosed as β thalassaemia trait Extensive studies of the polymorphic sites within the β globin gene cluster in all the members of the family resulted in the conclusion that the paternal chromosome 11 of the newborn was different from that expected. Paternity was confirmed by HLA typing and blood group studies. The analysis of another polymorphic locus on chromosome 11 within the family was in agreement with the possibility of a crossing over between the two paternal chromosomes in a region 5' to the β gene, previously indicated to contain a 'hot spot' area for recombination. This report underlines the risk of performing prenatal diagnosis using restriction polymorphisms 5' to the β gene.