# Autosomal Dominant Pedigree Analyzer 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. > Canonical page: https://elysiatools.com/en/tools/autosomal-dominant-pedigree - **Category:** Education - **Keywords:** autosomal dominant, dominant pedigree analysis, pedigree calculator, vertical transmission, male to male transmission, huntington inheritance, achondroplasia inheritance, 3:1 ratio, genetic pedigree, mendelian inheritance, genetics ## Overview The Autosomal Dominant Pedigree Analyzer calculates expected offspring risk from parental genotypes, compares observed affected and unaffected children with the expected ratio using a chi-square test, and checks whether male-to-male transmission supports autosomal rather than X-linked dominant inheritance. ## Inputs - **Parent 1 Status** (select): Genotype status of the first parent. - **Parent 2 Status** (select): Genotype status of the second parent. - **Affected children** (number): Number of affected children observed in the sibship. - **Unaffected children** (number): Number of unaffected children observed in the sibship. - **Male-to-male transmission observed** (checkbox): Whether an affected father has an affected son (rules out X-linked dominant inheritance). - **Decimal Places** (number) ## When to use - Estimate the expected affected-child proportion for AA, Aa, and aa parental genotype combinations. - Check whether observed sibling counts fit an expected 1:1, 3:1, all-affected, or unaffected outcome. - Evaluate male-to-male transmission as a pedigree clue that rules out X-linked dominant inheritance. ## How it works - Select the genotype status of each parent: affected heterozygous (Aa), affected homozygous (AA), or unaffected (aa). - Enter the observed numbers of affected and unaffected children. - Indicate whether an affected father has an affected son, and choose the number of decimal places. - Review the expected ratio, per-child risk, chi-square result, and inheritance-pattern note. ## Use cases - Practice Mendelian inheritance calculations for autosomal dominant traits. - Compare classroom pedigree observations with expected 1:1 or 3:1 ratios. - Assess whether father-to-son transmission supports an autosomal inheritance pattern. ## Frequently asked questions ### What offspring risks does the analyzer calculate? Aa × aa gives 50%, Aa × Aa gives 75%, AA × any genotype gives 100%, and aa × aa gives 0% affected offspring. ### What does the chi-square result show? It indicates whether the observed affected and unaffected counts fit the ratio expected from the selected parental genotypes. ### Why is male-to-male transmission important? An affected father passing the trait to a son rules out X-linked dominant inheritance and is consistent with autosomal dominant inheritance. ### Does a 50% risk mean half of every family will be affected? No. It is the probability for each child, so small families may differ from the expected overall ratio. ### Can this tool provide a medical diagnosis? 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