Tuberous Sclerosis Complex

A 4-year-old girl is brought to the pediatric clinic by her mother with a history of infantile spasms controlled on vigabatrin since age 8 months. On examination, you note hypomelanotic macules on her trunk (accentuated under Wood's lamp), facial angiofibromas over the malar regions, and a shagreen patch on the lumbosacral skin. Brain MRI shows multiple cortical tubers and a small subependymal nodule. The inheritance pattern shown as **A** in the diagram best describes the genetic basis of this child's condition. Which of the following statements about this inheritance pattern is most consistent with the clinical presentation in this case?