Chromosomal organization of the amplified esterase B1 gene in organophosphate-resistant Culex pipiens quinquefasciatus Say (Diptera, Culicidae).

In Culex pipiens quinquefasciatus from California, high resistance to organophosphorus insecticides is due to an increased production of the detoxifying esterase B1 resulting from a 250-fold amplification of the structural gene. The chromosomal organization of this amplified gene was studied by in situ hybridization techniques. Esterase B1 gene copies were found to be clustered on a single chromosome, tentatively identified as chromosome II.