- Polymorphism in the coding part of the sterol 12alpha-hydroxylase gene does not explain the marked differences in the ratio of cholic acid and chenodeoxycholic acid in human bile. Abrahamsson, A., Gåfvels, M., Reihnér, E., Björkhem, I., Einarsson, C., Eggertsen, G. Scand. J. Clin. Lab. Invest. (2005)