Final answer:
Maternal transmission in mitochondrial inheritance is exemplified by Leber's hereditary optic neuropathy, where mutations in the mitochondrial DNA are passed from mother to child, unlike autosomal or X-linked recessive conditions like cystic fibrosis and Duchenne muscular dystrophy that involve genes from both parents.
Step-by-step explanation:
In mitochondrial inheritance, maternal transmission refers to genes that are passed down from the mother through the mitochondria, which have their own DNA separate from the nuclear DNA. The correct answer to the question of which disease is an example of maternal transmission is (a) Leber 's hereditary optic neuropathy. This condition is maternally inherited because the mutations causing this disease are found in the mitochondrial DNA, which is exclusively inherited from the mother.
In contrast, diseases like Duchenne muscular dystrophy, Huntington's disease, and cystic fibrosis are not examples of mitochondrial inheritance. Duchenne muscular dystrophy and other X-linked recessive diseases, such as color blindness and hemophilia, are typically passed down from carrier mothers to their sons, whose condition is affected due to having one X chromosome. Conditions like cystic fibrosis and Huntington's disease involve autosomal inheritance, where genes from both mother and father contribute to the offspring's genetic makeup.