Novel genes have been isolated which encode cytochrome P450 and NADPH reductase enzymes of the .omega.-hydroxylase complex of C. tropicalis 20336. Vectors including these genes, transfected host cells and transformed host cells are provided. Methods of producing of cytochrome P450 and NADPH reductase enzymes are also provided which involve transforming a host cell with a gene encoding these enzymes and culturing the cells. Methods of increasing the production of a dicarboxylic acid and methods of increasing production of the aforementioned enzymes are also provided which involve increasing in the host cell the number of genes encoding these enzymes. A method for discriminating members of a gene family by quantifying the expression of genes is also provided.