Pedigree Chart Analyzer
Answer a short series of questions about how a trait appears across a family's generations — whether it skips generations, and whether it shows a sex bias — to infer its most likely inheritance pattern: autosomal dominant, autosomal recessive, X-linked dominant, or X-linked recessive. Two 3D diagrams compare a trait appearing every generation to one skipping a generation, and charts summarize the four classic inheritance patterns.
Reviewed by the ToolNestr Editorial Team — July 2026
1. Do two unaffected parents ever have an affected child (does the trait skip generations)?
2. Does the trait affect males and females in roughly equal numbers?
3. Do all daughters of an affected father show the trait, while none of his sons ever do?
Every generation vs. skipping a generation
1. Appears every generation
Every affected individual (amber) has an affected parent — consistent with dominant inheritance.
2. Skips a generation
Unaffected carriers (grey) hide the trait for a generation — consistent with recessive inheritance.
Inheritance pattern reference charts
How it works
The core idea in one line: each of the four classic inheritance patterns leaves its own distinctive fingerprint across a family tree — whether the trait can hide for a generation, and whether it favors one sex — so a couple of well-chosen yes/no questions about a pedigree is usually enough to identify which one is at work.
Skips generations? → Recessive; Never skips? → Dominant
the first branching question
Equal sex distribution? → Autosomal; Sex-biased, no father-to-son transmission? → X-linked
the second branching question
A recessive trait can hide silently in unaffected carriers for a generation before reappearing, while a dominant trait generally can't — every affected individual needs an affected parent. Separately, an autosomal trait (on one of the 22 non-sex chromosomes) affects both sexes equally, while an X-linked trait rides along on the X chromosome, producing a very different, sex-biased inheritance pattern — most distinctively, an affected father can never pass an X-linked trait to his sons, since sons always inherit his Y chromosome instead. Combining the answer to just these two questions — does it skip generations, and does it show a sex bias — narrows a real pedigree down to one of the four classic Mendelian inheritance patterns.
Worked example 1 — cystic fibrosis (autosomal recessive)
Given: Two unaffected parents (both unknowing carriers) have a child with cystic fibrosis. The condition affects males and females in equal numbers across the population.
Cystic fibrosis is a textbook real-world example of autosomal recessive inheritance — both parents are unaffected carriers, each contributing one recessive allele.
Worked example 2 — hemophilia (X-linked recessive)
Given: An unaffected woman (a carrier) has an affected son and an unaffected daughter (who is herself a carrier). The condition affects far more males than females across the family.
Hemophilia's famous spread through European royal families, passed through unaffected carrier queens and princesses to affected sons and grandsons, is the classic historical example of this exact pattern.
The four classic inheritance patterns
Each pattern leaves a distinctive signature across a pedigree's generations.
| Pattern | Skips generations? | Sex distribution |
|---|---|---|
| Autosomal dominant | No | Equal |
| Autosomal recessive ★ | Yes | Equal |
| X-linked dominant | No | More affected females; affected fathers pass to all daughters, no sons |
| X-linked recessive | Yes | More affected males; never passes father to son |
★ Reference row (worked example 1). Skipping generations combined with equal sex distribution is the classic signature of autosomal recessive inheritance.
Where pedigree analysis actually matters
🏥 Genetic counseling
Genetic counselors construct and analyze real family pedigrees using exactly this logic to estimate the probability that future children will inherit a genetic condition.
🧬 Clinical diagnosis of inherited conditions
Recognizing a family's inheritance pattern helps clinicians narrow down which specific genetic condition (and which gene) might be responsible for a set of symptoms running in a family.
👑 Historical genetics (the "royal disease")
Hemophilia's spread through European royalty in the 19th and 20th centuries is one of history's best-documented real-world pedigrees, and remains a classic teaching example of X-linked recessive inheritance.
🐕 Veterinary and animal breeding genetics
Breeders use pedigree analysis to identify how inherited health conditions or desired traits are passed through breeding lines, guiding responsible breeding decisions.
Common misconceptions
"If a trait skips a generation, it must be recessive."
Skipping generations strongly suggests recessive inheritance, but it isn't absolute proof — reduced penetrance (a dominant allele not always producing the trait) can occasionally produce a similar-looking skipped pattern, though this is far less common than simple recessive inheritance.
"X-linked traits only ever affect males."
Females can absolutely be affected by X-linked traits — for a recessive X-linked trait, a female needs two copies (one from each parent) to be affected, which is less common than a male needing just one copy, but it does happen.
"A pedigree can prove with 100% certainty which inheritance pattern is responsible."
A pedigree pattern only shows what's most consistent with the observed data — genetic testing is required to confirm the exact gene and inheritance mechanism responsible, especially since small family pedigrees don't always show every possible combination of matings needed to rule out every alternative pattern.
"Every genetic trait follows one of these four simple patterns."
Many real traits are more complex — polygenic (influenced by multiple genes), influenced by environment, or showing incomplete dominance or codominance — the four classic Mendelian patterns analyzed here are the simplest and most commonly taught case, not the only possibility.
Formula sources & further reading
The formulas here are standard, traceable to:
- • OpenStax, Biology 2e — Chapter 12, "Mendel's Experiments and Heredity" (free, peer-reviewed, includes pedigree analysis). openstax.org
- • Klug, Cummings & Spencer, Concepts of Genetics — Pedigree analysis chapter.
- • Nussbaum, McInnes & Willard, Thompson & Thompson Genetics in Medicine — Clinical pedigree interpretation chapter.
A simplified decision tree covering the four classic Mendelian inheritance patterns. Real pedigree analysis in clinical genetics considers additional factors like penetrance and pedigree size.
How to use this calculator
Answer the generation-skipping question
Do two unaffected parents ever have an affected child?
Answer the sex-distribution question
Does the trait affect both sexes equally, or show a bias?
Read the inferred inheritance pattern
The most likely pattern displays automatically based on your answers.
Related tools
Frequently asked questions
What is a pedigree chart?
A pedigree chart is a family tree diagram showing which relatives are affected by a genetic trait across multiple generations, used to infer how that trait is inherited.
How do you tell if a trait is dominant or recessive from a pedigree?
If the trait "skips generations" — appearing in a grandparent, disappearing in the parents, then reappearing in a grandchild — it's almost always recessive. If every affected individual has at least one affected parent (no skipped generations), it's more likely dominant.
How do you tell if a trait is autosomal or X-linked?
If the trait affects males and females in roughly equal numbers, it's likely autosomal. If it strongly favors one sex (typically males) and never passes from an affected father directly to a son, that pattern points to X-linked inheritance.
Why does X-linked recessive inheritance affect more males than females?
Males have only one X chromosome, so a single copy of a recessive X-linked allele is enough to cause the trait. Females have two X chromosomes, so they need two copies (one from each parent) to be affected — making it much more likely for females to be unaffected carriers instead.
Why can't an affected father pass an X-linked trait to his sons?
A father passes his Y chromosome, not his X chromosome, to his sons — so an X-linked trait carried on the father's X chromosome can only be passed to his daughters, never directly to his sons.