The invention relates to a novel acetylcholinesterase gene (ace-1) responsible for resistance to organophosphorus and/or carbamates in mosquitoes, which is non-homologous to the D. melanogaster acetylcholinesterase gene (ace-2), products of the ace-1 gene (cDNA, protein AchE1) and the applications thereof, particularly for the screening of novel insecticides and the genetic detection of resistance to organophosphorus and/or carbamates in mosquito populations.