Résumé
Due to the high annual birth rate of thalassemia major in our country, its prevention by prenatal diagnosis is of important priority. Gene mutation remains unknown in 10-20% of thalassemia trait people in Iran. In these cases, linkage analysis using polymorphic sites which are located near or within the gene is necessary to follow the mutant or the normal chromosome. SspI polymorphic site which is studied for the first time in Iran is located in the second intron of beta globin gene. The aim of this study was to determine the polymorphism frequency of this site in Mazandaran province. Peripheral blood of 211 thalassemia trait patients living in Mazandaran province was collected. After DNA extraction and amplification of the beta globin gene region containing the SspI polymorphic site, the effect of SspI restriction enzyme was evaluated on agarose gel. In 422 analyzed chromosomes, 20.6% were negative for SspI polymorphic site. Negative sites were almost equally associated with normal and mutant alleles [11.9% and 14.3% respectively]. SspI site analysis can be applied to follow the normal or mutant alleles of beta globin gene