One of the parents of a cross has a mutation in its mitochondria....

Cytoplasmic inheritance or extranuclear inheritance is the transmission of genes that occur outside the nucleus such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria. In mammals, cytoplasmic genes are only contributed by female gamete, e.g., Male gamete only contribute its nuclear genes. Thus, none progenies would not inherit any mutated genes in mitochondria by father. Related Theory The phenotypes that are controlled by nuclear factors found in the cytoplasm of the female are said to express a maternal effect. Those phenotypes controlled by organelle genes exhibit maternal inheritance. The classic phenotype which exhibits maternal effects is coiling direction of snail shells.