Rapid differentiation of five common alpha-thalassemia genotypes by polymerase chain reaction

The alpha -thalassemias are common genetic disorders that arise from reduce d synthesis of the alpha -globin chains. At present, large-scale carrier sc reening and clinically valuable antenatal detection programs have not been established for the congenital disorder alpha -thalassemia (alpha -thal). W e have developed a simple nonradioactive polymerase chain reaction (PCR) ap proach that can detect and differentiate several common alpha -globin gene deletional alpha -thals regardless of the break points. When three primer s ets were used-two gene-specific sets for the alpha (1)- and alpha (2)-globi n genes and one set for the beta -actin gene (serving as an internal contro l)-PCR products from genomic DNA were simultaneously amplified and analyzed after coamplification and gel electrophoresis. The number of a-globin gene s present in the subjects was determined by the intensity of alpha (1) and alpha (2) bands normalized with that of beta -actin when using densitometry , Our results demonstrate that five common genotypes of deletional a-thal a re differentiated by the ratios of alpha (1)/beta -actin and alpha (2)/beta -actin. We also examined the feasibility of coupling this allele-specific amplification to a color-complementary assay. This easy and reproducible PC R assay is suitable for identifying a-thal carriers in screenings of large populations and improving genetic counseling.