- The three human cytochrome P450 lanosterol 14 alpha-demethylase (CYP51) genes reside on chromosomes 3, 7, and 13: structure of the two retrotransposed pseudogenes, association with a line-1 element, and evolution of the human CYP51 family. Rozman, D., Strömstedt, M., Waterman, M.R. Arch. Biochem. Biophys. (1996)