but can be suppressed by the other construct. In this way, individuals with only one of the two constructed genes (heterozygotes) are selected against, but homozygotes with both or neither construct are genetically healthy. Analysis of this model using simple population genetics shows that successful spread of refractory genes using this engineered underdominance is possible with relatively small release of the constructed genotype into the population. A similar system of manipulation of pest populations was achieved in a population of Drosophila melanogaster by using a knock-down/rescue system. The genetic construct in this system employs a dsRNAi knockdown of a C-reactive protein, RpL14, as well as a rescue element (a complete copy of the wild type RpL14 gene). Individuals that are heterozygous for this construct experience lowered fitness due to limited restoration of the RpL14 gene, which results in reduced female fertility and delayed development, along with various other mutations that ultimately lower fitness by 70-80%. This system of underdominance allowed manipulation of the population and ultimate fixation of the constructed genotype and has potential applications in a number of settings, including agriculture and the reduction of various pest-carried diseases. See also Natural selection Disruptive selection Heterozygote advantage Population genetics References External links Underdominance- ResearchGate The Biology Project Population Genetics The Stability of An Equilibrium and the Average Fitness of a Population Chromosome Inversions, Local Adaptations and Speciation Chromosomal Rearrangements cause Underdominant Pollen Sterility Classical genetics