Mitochondrial Inheritance on a Pedigree: Mother's Line Only
How mitochondrial inheritance shows up on pedigree charts: all children of an affected mother affected, fathers never transmit, and why the pattern looks like a maternal column.
- inheritance-patterns
- mitochondrial
- genetics-education
Mitochondrial DNA is inherited almost entirely from the mother — the egg contributes the mitochondria, the sperm contributes little. That single fact produces a pedigree pattern so distinctive you can recognize it without knowing any of the people.
The two rules
- All children of an affected mother are affected. Sons and daughters both.
- An affected father transmits nothing. His children are unaffected, because his sperm’s mitochondria don’t survive fertilization.
What the chart looks like
- The affected people form a maternal column: an affected woman, all her children, all her daughters’ children, and so on down the page.
- Affected males appear in every generation of that column, but none of their children are affected.
- The rest of the chart — the descendants of unaffected women — stays clean.
How it differs from X-linked dominant
Both patterns involve affected women transmitting to children, but the distinction is clean:
- Mitochondrial: affected fathers never have affected children.
- X-linked dominant: affected fathers have affected daughters (they pass their X to every daughter).
Look for an affected man with unaffected children to rule out X-linked dominant.
Reading it in practice
The mitochondrial template lays out the full pattern: a first-generation affected mother, an affected son and daughter, and the affected daughter’s children all shaded, while the son’s children — the first unaffected generation on the chart — stand out in contrast.
Try this in the maker: open the template, delete one person, and watch the chart still teach the pattern. The rule survives because it lives in the structure — which is exactly why pedigrees are drawn the way they are.