Duchenne-type muscular dystrophy is an inherited muscle disease due to a mutant form of the protein called dystrophin. The pattern of inheritance of the disease has these characteristics:
(1) affected males have unaffected children, (2) the unaffected sisters of affected males often have affected sons, and (3) the unaffected brothers of affected males have unaffected children.
What type of inheritance is suggested by these findings? Explain your reasoning. Make sure you include the conclusion you can draw from each observation.