Control of the microsomal mixed-function oxidase by Ox 2 and Ox 5 genes in houseflies

The microsomal mixed-function oxidase (MFO) in houseflies is controlled by two semidominant genes, Ox² and Ox⁵, situated on chromosomes 2 and 5, respectively. MFO controlled by these genes has almost similar affinity toward cyclodiene epoxidation, but only the one controlled by Ox⁵ can degrade DDT. A strain, YFc, homozygous for both oxidase genes shows twice as much MFO activity toward aldrin as either of the parent homozygotes, Fc or Y, but only as much activity toward DDT as the parent strain Fc. These Ox² and Ox⁵ genes in the YFc strain maintain their identity with regard to DDT in their hybrids with a susceptible homozygous strain recessive for the two oxidases as seen by segregation in the test-cross progenies. The Ox² gene is situated at 32 units from the Deh and car genes, 40 units from stw, and about 69 units from Mk. The Ox⁵ gene is situated at 40 units from the ocra gene and 82 units from apt on chromosome 5.