What are the hallmarks of X-linked recessive inheritance?
• As with any X-linked trait, the disease is never passed from father to son. • Males are much more likely to be affected than females. If affected males cannot reproduce, only males will be affected. • All affected males in a family are related through their mothers. • Trait or disease is typically passed from an affected grandfather, through his carrier daughters, to half of his grandsons. Counseling in X-linked recessive diseases is a bit more complex than it is in autosomal recessive diseases. In X-linked recessive diseases, Bayes theorem, or Bayesian probability must be used to accurately calculate carrier probabilities. In some pedigrees these probabilities change as new information appears. Sometimes we use Bayesian probability without recognizing it. Consider the following: A patient of yours is getting married and comes to you for counseling. She has a brother with a rare X-linked recessive disease. Her mother’s father also had the disease. She wants to know the probability of
