# Pedigree Probability Tree — Offspring Disease Risk Step-by-step Mendelian probability tree for pedigree problems: autosomal recessive P(affected) = carrier × carrier / 4, autosomal dominant both-affected 3/4, X-linked recessive carrier mother → 50% affected sons. Derived from Griffiths, Hartl & Clark 2007, StatPearls. Educational use only. > Canonical page: https://elysiatools.com/en/tools/pedigree-probability-tree - **Category:** Education - **Keywords:** pedigree analysis, pedigree probability, probability tree, offspring disease risk, autosomal recessive risk, autosomal dominant inheritance, x-linked recessive carrier, cystic fibrosis risk, hemophilia inheritance, carrier probability, mendelian inheritance, genetics ## Overview Pedigree Probability Tree calculates offspring disease and carrier probabilities using Mendelian inheritance models. Choose autosomal recessive, autosomal dominant, or X-linked recessive inheritance, enter the father's and mother's probabilities, and receive a step-by-step probability result in JSON format. Educational use only. ## Inputs - **Inheritance Mode** (select): Autosomal recessive: probabilities are carrier probabilities. Autosomal dominant: probabilities of being affected (heterozygous). X-linked recessive: father = probability affected, mother = probability carrier. - **Father Carrier/Affected Probability** (number): Recessive: P(father is a carrier). Dominant: P(father is affected, heterozygous Aa). X-linked recessive: P(father is affected). - **Mother Carrier/Affected Probability** (number): Recessive: P(mother is a carrier). Dominant: P(mother is affected, heterozygous Aa). X-linked recessive: P(mother is a carrier). - **Decimal Places** (number) ## When to use - Estimate affected-child and carrier probabilities for autosomal recessive pedigrees. - Calculate inheritance risk when both parents are affected heterozygotes under an autosomal dominant model. - Break down affected-son, affected-daughter, and carrier-daughter probabilities for X-linked recessive inheritance. ## How it works - Select an inheritance mode: autosomal recessive, autosomal dominant, or X-linked recessive. - Enter the father's and mother's carrier or affected probabilities according to the selected mode. - The tool applies Mendelian probability rules to calculate the relevant offspring outcomes. - Choose the number of decimal places and review the returned result and probability breakdown. ## Use cases - Teaching Mendelian inheritance with transparent probability-tree calculations. - Checking pedigree exercises involving cystic fibrosis or other autosomal recessive traits. - Studying sex-specific inheritance patterns such as hemophilia or color blindness. ## Frequently asked questions ### What inheritance patterns does the tool support? It supports autosomal recessive, autosomal dominant, and X-linked recessive inheritance. ### What do the parent probability fields mean? Their meaning depends on the selected mode: carrier probability for recessive models and affected probability for the dominant model. ### What does the autosomal recessive calculation return? It returns the probabilities of an affected child, a carrier child, and an unaffected non-carrier child. ### How does the X-linked recessive model report results? It reports overall affected-child probability plus separate affected-son, affected-daughter, and carrier-daughter probabilities. ### Can this replace genetic counseling? No. The calculator is for educational use and does not replace professional genetic counseling or medical advice. ## Related tools - [Autosomal Dominant Pedigree Analyzer](https://elysiatools.com/en/tools/autosomal-dominant-pedigree): Compute AD offspring risk (Aa×aa 1:1, Aa×Aa 3:1, AA×any all affected), chi-square fit of observed children, and hallmark checks including male-to-male transmission that rules out X-linked dominant. Derived from Griffiths, Hartl & Clark 2007, StatPearls, OMIM. Educational use only. - [Inbreeding Coefficient Calculator (Wright's F)](https://elysiatools.com/en/tools/inbreeding-coefficient): Compute Wright's F = Σ (1/2)^(n1+n2+1)(1+F_A) over common-ancestor paths, with reference values (full sib 0.25, half sib 0.125, first cousins 0.0625) and elevated recessive risk q² + F·q·(1−q). Derived from Wright 1922, Falconer & Mackay, Hartl & Clark 2007, StatPearls. 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Any recessive offspring proves heterozygous; zero recessive suggests homozygous with P = 0.5^n. Derived from Mendel 1866, Griffiths, Hartl & Clark 2007, StatPearls. Educational use only. - [PCR Annealing Temperature Calculator (Ta = Tm − 5°C)](https://elysiatools.com/en/tools/annealing-temperature-calculator): PCR Ta by the simple rule (lower primer Tm − 5°C) or the Rychlik 1990 formula (0.3·Tm_primer + 0.7·Tm_product − 14.9), with a ±3°C gradient window and primer-Tm mismatch warning. Derived from Rychlik 1990, Innis & Gelfand 1990, Lorenz 2012. Lab-planning use only. - [Autosomal Recessive Inheritance Risk Calculator](https://elysiatools.com/en/tools/autosomal-recessive-risk): Compute per-child and cumulative autosomal recessive disease risk from parental statuses (carrier / affected / non-carrier / unknown via population carrier rate), including the 2/3 carrier rule. Derived from Griffiths, Hartl & Clark 2007, StatPearls. 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