Demonstration of two alpha-globin genes per human haploid genome for normals and Hb J Mexico.

Complementary DNA (cDNA) was prepared with viral RNA-dependent DNA polymerase using human globin messenger RNA (mRNA) as template. By selective hydridization to globin mRNA from beta-thalassaemics a probe which was greater than 85% complementary to alpha-globin mRNA was purified. This was hybridized in cDNA excess to human genomic DNA, and the rate and extent of hybridization confirmed that there are two genes for alpha-globin per haploid genome. Cellular DNA was also prepared from peripheral blood from cases expressing the alpha-globin chain mutant Hb J Mexico to varying extents. This DNA was identical in hybridization behaviour to normal DNA demonstrating that the imbalanced mutant chain synthesis seen physiologically is not due to a gene deletion.