theory.toys – Pedigree Inheritance Analysis

Inheritance Mode

Autosomal recessive Autosomal dominant

X-linked recessive 🔑 Unlock

Pedigree Template

Select pedigree:

Population Parameters

Carrier frequency (q): 0.02

Disease prevalence: 0.04%
(assumes Hardy-Weinberg equilibrium)

Click Individuals

Click on individuals to toggle affected status

Display Options

Show genotype probabilities Show legend

Pedigree Analysis

Pedigree analysis traces the inheritance of genetic traits through families. By analyzing who is affected, we can infer inheritance patterns and calculate the probability that specific individuals are carriers or will be affected.

Inheritance Patterns

Autosomal recessive: Trait appears in both sexes. Affected individuals have two recessive alleles (aa). Parents are often carriers (Aa) and unaffected. Can skip generations.
Autosomal dominant: Trait appears in both sexes. Affected individuals have at least one dominant allele (AA or Aa). Does not skip generations—every affected person has an affected parent.
X-linked recessive: Primarily affects males. Carrier females (X^{A^{X^a⁾}} are usually unaffected but can pass the trait to sons. Affected males (X^{a^Y)} cannot pass the trait to sons, only to daughters who become carriers.

Pedigree Symbols

Circle: Female
Square: Male
Filled symbol: Affected individual (expresses the trait)
Half-filled: Carrier (heterozygous for recessive trait)
Horizontal line: Mating/marriage
Vertical line: Offspring connection

Calculating Probabilities

For each individual, we calculate genotype probabilities based on:

Their phenotype (affected or unaffected)
Their parents' genotypes (if known or inferred)
Population allele frequencies (Hardy-Weinberg equilibrium)
The mode of inheritance

Consanguinity

Consanguineous marriages (between relatives) increase the probability of recessive genetic disorders because related individuals are more likely to carry the same rare recessive alleles inherited from a common ancestor.