Medical Genetics Characteristics Unlike nuclear genes, which are inherited from both parents, mitochondrial genes are inherited only from the mother In mammals, 99. 99% of mitochondrial DNA(mtDNA) is inherited from the mother This is because the sperm carries its mitochondria around a portion of its tail and has only about 100 mitochondria compared to 100,000 in the oocyteMedical Genetics Characteristics Unlike nuclear genes, which are inherited from both parents, mitochondrial genes are inherited only from the mother. In mammals, 99.99% of mitochondrial DNA (mtDNA) is inherited from the mother. This is because the sperm carries its mitochondria around a portion of its tail and has only about 100 mitochondria compared to 100,000 in the oocyte