Independent recombination events between the duplicated human {alpha} globin genes; implications for their concerted evolution

We have examined the molecular structure of the human α globin gene complex from individuals with a common form of a thalassaemia in which one of the duplicated pair of α genes (αα) has been deleted (−α3·7). Restriction mapping and DNA sequence analysis of the mutants indicate that different −α3·7 chromosomes are the result of at least three independent events. In each case the genetic crossover has occurred within a region of complete homology between the α1 and α2 genes. Since the −α chromosomes may reflect the processes of crossover fixation and gene conversion between the two genes, their structures may provide some insight into the mechanism by which the concerted evolution of the human α globin genes occurs.