How does mitochondrial inheritance differ from nuclear inheritance?

Mitochondrial inheritance is distinct from nuclear inheritance primarily due to the maternal-only transmission of mitochondrial genes. Mitochondria, which are the energy-producing organelles in cells, possess their own circular DNA separate from nuclear DNA. When fertilization occurs, the sperm contributes nuclear DNA to the zygote, but mitochondria from the sperm are typically destroyed soon after fertilization. As a result, the zygote—and subsequently all the cells in the organism—inherits its mitochondria solely from the egg, making mitochondrial genes maternally inherited.

This mode of inheritance has significant implications for how certain traits and conditions are passed on through generations. For many mitochondrial disorders, a mother who carries a mutation in her mitochondrial DNA can pass that pathology to all of her offspring, while fathers do not contribute to the mitochondrial gene pool, making this inheritance pattern unique compared to nuclear genes that are inherited from both parents.

The other options are misleading; mitochondrial genes are not always inactive, the structure and replication of mitochondrial DNA differ from nuclear genes, and yet both types tend to have different mutation rates that aren't strictly tied to this scenario being slower for mitochondrial genes.