Parents of a toddler are dismayed when they learn that their child has Duchenne's muscular dystrophy. Which statement describes the inheritance pattern of the disorder?

B The disorder is caused by an over-replication of the X chromosome in males. D The affected gene is located on the X chromosome of the mother. A An affected gene is located on one of the 21 pairs of autosomes. C The affected gene is located on the Y chromosome of the father.