Inheritance Patterns

Autosomal dominant inheritance

Autosomal Dominant Inheritance

  • Individuals affected in every generation
  • Some carriers may not manifest disease
  • Males and females have equal chance of passing on mutation
  • 50% risk to children

Autosomal recessive inheritance graphic

Autosomal Recessive Inheritance

  • May be only one generation affected
  • Carriers typically do not have condition
  • Both parents must be carriers of the mutation
  • 25% risk to children

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X-linked Inheritance

  • No male-to-male transmission
  • Though rare, females can be affected if they inherited two mutations
  • Many female carriers (one mutation) will have no symptoms; those that do have milder symptoms than seen in males
  • Risk for inheriting an X-linked condition:
    • 100% for daughters of affected fathers to be carriers
    • 0% for sons of affected fathers to be affected
    • 50% for daughters of carrier or affected mothers to be carriers
    • 100% for sons of affected mothers to be affected
    • 50% for sons of carrier mothers to be affected

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Complex Inheritance

  • No clear Mendelian pattern of inheritance
  • Clustering of biologically related conditions in the family
  • Risk estimates based primarily on empiric data
  • The chance of developing a complex trait depends on several factors, which may include:
    • The number of relatives affected with a condition (or related conditions)
    • How closely one is related to the affected individual(s)
    • Similarity of the shared environment and lifestyle factors
    • Severity of the condition in the affected relative
    • The age at onset in the affected family member
    • The sex of the affected family member
    • Ethnicity

    Reviewed June 2023