Benzene induces gene-duplicating but not gene-activating mutations at the glycophorin A locus in exposed humans

In human bone marrow cells, benzene develops gene-duplicating mutations at the glycophorin A (GPA) locus. Enhanced exposure to benzene increases the cell frequency of the surface protein with double N expression (NN), but not of the surface protein with single N. Duplication of the N allele and loss of the GPA M allele produces the NN variant. The surface protein with single N allele results from gene inactivation.