Smith-Magenis Syndrome (RAI1)

A 3-year-old boy presents with moderate intellectual disability, distinctive facial features (brachycephaly, broad square face, deep-set eyes, tented upper lip), and a striking behavioral phenotype including severe sleep disturbance with daytime somnolence and nighttime awakening. His parents are unaffected and non-consanguineous. Chromosomal microarray reveals a heterozygous interstitial microdeletion at 17p11.2 encompassing the RAI1 gene, as marked **A** in the inheritance diagram. Which of the following best describes the inheritance pattern and recurrence risk in this family?