Availability of competent mosquito vectors is critically necessary for the maintenance and spread of the pathogens causing malaria, lymphatic filariasis, and more. Mosquitoes can be genetically engineered for resistance to parasite development and, with the suitable driving mechanism, can drive parasite resistance genes into wild, susceptible vectors in areas of endemic infection to lower the intensity of transmission. An outstanding model organism for vector biology research is Aedes aegypti. A strong genetic linkage map based on random amplified polymorphic DNA from PCR (RAPD-PCR) also has been constructed for A. aegypti. The availability of molecular genetic linkage maps has allowed researchers to begin to address the genetic complexity of certain aspects of vector competence. The first such study evaluated the genetic control of susceptibility of Aedes aegypti to infection with the human pathogen B. malayi. According to the findings, vector competence for DEN in Aedes is controlled at least by two genes. One gene or group of genes regulates a midgut infection barrier, while the other controls a midgut escape barrier keeping the infection from spreading. Finding if selection techniques employed in the laboratory could generate parasite strains able to develop in the refractory strains of mosquitoes used before in genetic mapping studies would also be fascinating and important. If successful, one would expect that subsequent QTL mapping for susceptibility to the new parasite strain would identify different or more loci within the mosquito genome.