Pedigree Chart Worksheet Generator
Each sheet is a three-generation family drawn the usual way — squares for males, circles for females, filled for affected — simulated under autosomal dominant, autosomal recessive, X-linked dominant or X-linked recessive inheritance. The question is which of the four could explain it. The answer for each mode comes from searching every combination of genotypes for the whole family, and where one couple and their children already rule a mode out, the answer names them. When exactly one mode fits, a second question asks for a genotype that every fitting combination agrees on.
What this generator does
Draws an invented family of up to 16 people, asks which modes of inheritance could explain it, and answers each mode with a reason, plus a genotype question when one mode alone fits.
How to use this tool
- Choose the inheritance to simulate, or any, and whether exactly one mode or up to two may fit.
- Press Make a pedigree, work out the answer, then open Answers.
- Print the pedigree and questions with the answer page.
Understanding the controls
- Simulated inheritance
- Autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, or any one of them at random.
- Modes that may fit
- Exactly one, or up to two. With exactly one, families are autosomal; X-linked choices always allow two.
- Paper and seed
- Paper size for printing; a seed with the same settings rebuilds the same family while the generator is unchanged.
Worked examples
- Any mode, exactly one fits, seed ‘garden’
- Fourteen people, I-2 and III-2 affected. Only autosomal recessive fits; the family of II-1 and II-2 rules out both dominant modes, and that of I-1 and I-2 rules out X-linked recessive. II-1 must be Tt.
- X-linked recessive, seed ‘garden’
- Fourteen people, III-5 and III-7 affected. Autosomal recessive and X-linked recessive both fit; the dominant modes are ruled out by one family.
- Why X-linked sheets allow two modes
- In 30 tries per mode, no X-linked family of this size fitted only its own mode: an autosomal mode always fitted too, so the page lets two fit when X-linked is chosen.
Common use cases
- Pedigree analysis practice in a genetics topic
- A starter: rule out dominant modes from one family
- Revision of carriers and X-linked inheritance
How this generator works
The family is simulated: two founders, three or four children, two of whom have partners from outside the family and two to four children each. Genotypes pass from parents to children by Mendel's rules under the chosen mode. Then the simulation is set aside, and each mode is tested from the drawing alone: a search tries genotypes parents-first and keeps any combination that gives everyone their shown phenotype. A mode fits if any combination survives. A genotype is asked for only when every surviving combination gives that person the same one. Assumptions, stated on the sheet: full penetrance, no new mutations, partners unrelated to the family.
Randomness and fairness
Families are simulated with the browser's cryptographically secure generator, or from one seeded draw when a seed is typed. Seeded sheets are deterministic, not cryptographic. Which modes fit is computed, not random.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- The families and the trait are invented. Real pedigrees include incomplete penetrance, new mutations and related partners, which these sheets leave out on purpose.
- Families are small, so more than one mode often fits; the answers say so rather than picking one.
- Mitochondrial and Y-linked inheritance are not included.
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