Mitochondrial inheritance vs Mendelian inheritance
How to tell Mitochondrial inheritance and Mendelian inheritance apart when a board question makes them look alike.
Mitochondrial disease is maternal-only transmission with heteroplasmy; Mendelian disease follows nuclear pedigree rules.
Side by side
Mitochondrial inheritance shows maternal transmission to all children of affected mothers, variable expression from heteroplasmy, and disease in high-energy tissues.
Mendelian inheritance follows nuclear DNA patterns such as autosomal dominant, autosomal recessive, X-linked, or mitochondrial-independent pedigree ratios.
Mitochondria and their genome are inherited primarily from the oocyte cytoplasm, and heteroplasmy creates threshold effects.
Nuclear alleles segregate through meiosis with predictable dominance, recessiveness, sex linkage, and penetrance patterns.
Affected mother transmitting to sons and daughters, with affected fathers transmitting to none, supports mitochondrial inheritance.
Vertical dominant pattern, sibling recurrence from carrier parents, or sex-linked male predominance supports Mendelian inheritance.
The trap
Multiple affected generations are not automatically autosomal dominant; check whether affected fathers transmit disease.
The repair move
For pedigrees, check father-to-child transmission before deciding mitochondrial versus nuclear inheritance.
Try a free question
CoreA pedigree shows a family with progressive vision loss due to optic atrophy. All children (both sons and daughters) of affected mothers are affected. NONE of the children of affected fathers are affected. Variable severity is seen among siblings. Which pattern of inheritance is most likely?
Show answer and explanation
Answer: A. Mitochondrial inheritance. Mitochondrial inheritance: ALL children of affected mothers are at risk (mitochondria come from the oocyte), NONE of children of affected fathers are affected, variable severity reflects heteroplasmy. Leber hereditary optic neuropathy is a classic example.
Why the other choices are tempting
- B. Autosomal dominant inheritance allows father-to-son transmission, which is not seen here.
- C. Autosomal recessive inheritance shows affected siblings of unaffected parents, not the strict maternal transmission pattern.
- D. X-linked recessive inheritance affects predominantly males through carrier mothers, not all children of affected mothers.
- E. X-linked dominant inheritance has affected fathers transmitting to all daughters but not sons, the opposite of this pedigree's pattern.
Flashcards
Tap a card to flip it.
What clue supports Mitochondrial inheritance?
Choose Mitochondrial inheritance when the stem gives this pattern: Mitochondrial inheritance shows maternal transmission to all children of affected mothers, variable expression from heteroplasmy, and disease in high-energy tissues.
What clue supports Mendelian inheritance?
Choose Mendelian inheritance when the stem gives this contrasting pattern: Mendelian inheritance follows nuclear DNA patterns such as autosomal dominant, autosomal recessive, X-linked, or mitochondrial-independent pedigree ratios.
Quick answers
What is the fastest way to tell Mitochondrial inheritance from Mendelian inheritance?
Mitochondrial disease is maternal-only transmission with heteroplasmy; Mendelian disease follows nuclear pedigree rules.
What is the key clue for Mitochondrial inheritance?
Mitochondrial inheritance shows maternal transmission to all children of affected mothers, variable expression from heteroplasmy, and disease in high-energy tissues.
What is the key clue for Mendelian inheritance?
Mendelian inheritance follows nuclear DNA patterns such as autosomal dominant, autosomal recessive, X-linked, or mitochondrial-independent pedigree ratios.
What is the common trap with Mitochondrial inheritance vs Mendelian inheritance?
Multiple affected generations are not automatically autosomal dominant; check whether affected fathers transmit disease.