A 15 year-old African American boy presents to the emergency department complaining of severe pain in both legs and back. He climbed Mount Davis, the highest point in Pennsylvania (3213 ft) over the weekend. He reports that he enjoyed climbing the mount. As he was descending, he developed pain in his chest, legs and back. The pain has been present for 1 day and is steadily increasing in severity. He took ‘tons of tylenol and ibuprofen, and it ain’t cut it’. He denies any recent trauma. Since his pain started he feels like he should have listened to his parents, who warned him against the mountain trip because of a preexisting condition he has. He reports that he has suffered from severe bouts of chest pain, back pain and leg pain in the past when he engaged in multiple sporting events during the summer holidays. One of his cousins suffers from a similar disorder. On physical examination, he is afebrile and in some distress due to pain. He has nonspecific bilateral anterior thigh pain with no abnormalities appreciated. The remainder of his examination is normal. Laboratory tests reveal his hemoglobin level as 7.1 g/dL. Peripheral smear shows crescent shaped red blood cells. Of the following, which best describes the inheritance of this disorder?
