Practice question

Mitochondrial genome resides in cytoplasm and is maternally inherited because oocyte contributes abundant cytoplasm containing mitochondria while sperm mitochondria are generally degraded post-fertilization or outnumbered. Mother transmits mtDNA to all sons and all daughters equally, but only daughters pass it further to their offspring, creating distinct matrilineal pedigree with affected mothers transmitting to all children. Both sexes can be affected clinically, yet affected males never transmit to offspring. This pattern explains inheritance of myopathies, Leber hereditary optic neuropathy, and variable expression due to heteroplasmy.