A 28-year-old Indian man presents to the fertility clinic with primary infertility. His wife has been unable to conceive after 3 years of unprotected intercourse. Semen analysis reveals azoospermia. His father had a similar history of infertility and fathered him via assisted reproductive technology (ART). The pedigree shows that his paternal grandfather was also infertile, and this trait has affected only males in the paternal lineage for three generations with no skipped generations. The structure marked **A** in the pedigree diagram represents the inheritance pattern observed in this family. Y-microdeletion analysis confirms a deletion in the AZFc region. Which of the following best describes the inheritance pattern and its key feature marked **A**?