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A set of allele-specific oligonucleotide （ASO） probes used for detecting all 18 β-tha-lassemia mutations found in Chinese was immobilized on two strips of Biodyne C membrane;one containing 7 pairs of oligonucleotide probes specific for the most commonly found mutant al-leles

and the other containing the remaining 11 pairs of ASO

s

specific for the less commonlyfound.The membranes were hybridized with β-globin sequences amplified by polymerase chainreaction （PCR） with biotinylated primers

and then treated with Streptavidin-POD conjugateand substrates for color development.The method has been applied successfully to the detectionof all 18 Chinese β-thalassemia mutations and prenatal diagnosis of two high-risk pregnancies ofβ-thalassemia.Patients with homozygous

heterozygous and compound heterozygous alleles ofthese mutations and normal individuals could be easily distinguished by the present method.Us-ing the immobilized-probe format （reverse dot blot）

it was able to screen simultaneously multi-ple β-thalassemia mutations of a DNA sample by performing hybridization only once.This assayis simple

rapid and independent of radio-isotopes and can be appplied for all 18 β-thalassemiamutations so far found in Chinese population.It is considered that this method may be usefulfor gene frequency investigation of large numbers of β-thalassemia DNA samples and used as aroutine method in the clinic laboratory.