A 32-year-old woman with Leber hereditary optic neuropathy (LHON) due to a mitochondrial DNA mutation presents to the genetics clinic for family counseling. She has two healthy children from her affected partner, who also carries the same mtDNA mutation. The pedigree diagram shows the inheritance pattern of mitochondrial diseases. The feature marked **B** in the diagram — "No Transmission from Affected Father" — is a critical distinguishing characteristic of mitochondrial inheritance. Which of the following best explains why an affected father CANNOT transmit his mitochondrial disease to any of his children?