X linked or autosomal recessive? A new approach to an old problem.

Families in which a single male is affected with a disease which might be either X linked recessive or autosomal recessive present problems in counselling. Before female relatives can be counselled, the probabilities of each mode of inheritance must be assessed, taking into account the prior probabilities, the pedigree structure, any DNA probe data, and any carrier testing data. The widely used linkage analysis package LINKAGE can be used to do the calculation, which is much simpler than the conventional Bayesian method.