Abstract: An engineered genetic incompatibility (EGI) strain of a wild-type organism is designed to include a haplosufficient lethal allele and a haploinsufficient resistance allele. In another aspect, a biocontainment system generally includes a polynucleotide that encodes a coding region whose expression causes infertility or death, a transcription regulatory region operably linked upstream of the coding region and containing a silent mutation, and a polynucleotide that encodes a programmable transcription activator. The programmable transcription activator is engineered to bind to the transcription regulatory region in the absence of the silent mutation, thereby expressing the coding region in the absence of the silent mutation, but does not initiate expression of the coding region when the transcription regulatory region comprises the silent mutation.