Diversity of human gamma-globin gene loci including a quadruplicated arrangement.

A quadruplicated gamma-globin gene as a (5'-G gamma-gamma-gamma-A gamma-3') was detected in an adult Chinese during a survey designed to detect G gamma- and A gamma-globin genes in Japanese. Five triplicated (-G gamma-gamma-A gamma-) and two single (-gamma-) haplotypes were also detected in 103 healthy adult Japanese. All of the unusual chromosomes appeared to reflect an unequal but homologous crossover between G gamma- and A gamma-globin genes. A new Bgl II polymorphic site located around the 3' terminal region of the G gamma-globin gene was also discovered.