There are traits manifested in certain eukaryotes that result from extranuclear inheritance. The mitochondria, for instance, contain genetic material independent of the chromosomes inside the nucleus.
During the union of gametes, the mitochondrial DNA from the maternal parent is imparted to its offspring. Hence, when the mitochondrial DNA is expressed the resulting traits would be extranuclear in nature, and determined largely as maternal effect. Inherited diseases relating to mitochondria is called mitochondrial disease.