Inheritance Pattern Analyzer

A single copy of the mutant allele is sufficient to cause the phenotype.

• Affects males and females equally
• Appears in every generation (vertical transmission)
• Affected individuals usually have an affected parent
• 50% risk for children of affected individuals
• Unaffected individuals do not transmit the trait

Examples: Huntington's disease, Marfan syndrome, Achondroplasia

Two copies of the mutant allele are required for the phenotype.

• Affects males and females equally
• Often skips generations (horizontal pattern)
• Parents of affected are usually carriers
• 25% risk when both parents are carriers
• More common with consanguinity

Examples: Cystic fibrosis, Sickle cell anemia, PKU

The mutant allele is on the X chromosome; males are more frequently affected.

• Primarily affects males
• Females are usually carriers
• No male-to-male transmission
• Affected males have carrier mothers
• 50% of sons of carrier mothers are affected

Examples: Hemophilia, Duchenne muscular dystrophy, Red-green color blindness

A single copy of the mutant allele on X causes the phenotype.

• Affects females more than males
• May be lethal in males
• All daughters of affected males are affected
• No male-to-male transmission
• 50% of children of affected females are affected

Examples: Rett syndrome, Incontinentia pigmenti, Fragile X syndrome

Mitochondrial DNA is inherited exclusively from the mother.

• Affects both males and females
• Transmitted only by mothers
• All children of affected mothers may be affected
• Variable expression due to heteroplasmy
• Affected males cannot transmit

Examples: MELAS, MERRF, Leber hereditary optic neuropathy