Which inheritance pattern explains maternal transmission of a mitochondrial disorder?

• A. Autosomal dominant
• B. X-linked recessive
• C. Mitochondrial (maternal)
• D. Y-linked

Answer: (C)

Mitochondrial disorders show maternal transmission because mitochondria and their DNA come from the mother through the egg’s cytoplasm. Each child inherits the mother’s mitochondrial DNA, so an affected mother can pass the mutation to all of her children (both sons and daughters), while fathers do not pass mitochondria to their offspring. The severity among offspring can vary because cells can contain a mix of normal and mutated mitochondria (heteroplasmy), leading to different clinical expressions even within the same family. This pattern stands in contrast to autosomal dominant, X-linked recessive, or Y-linked inheritance, which involve different transmission routes and would not produce this strictly maternal pattern.