[Simple method of risk calculation in X-linked diseases].

The estimation of genetic risks in X-linked recessive disorders is a special case of Bayesian approach to probability calculation. Computing directly an estimation of the inverse of the risk is easier in this particular situation of only two mutually exclusive hypothesis: this function can be written in the form T = 1 + (To -1) X R, where R is a product of likehood ratios. The ratio of two probability density function represent a single factor, which is more manipulatable than the two components of the classical method.