Pedigree Charts Visualize Genetic Inheritance
- Pedigree charts allow us to map patterns of inheritance, revealing whether traits are dominant, recessive, autosomal, or sex-linked.
- They are especially useful for investigating genetic disorders in humans, where controlled breeding experiments are not possible.
Definition
Pedigree charts
Pedigree charts are family tree diagrams that track the inheritance of traits across generations.
Symbols and Conventions in Pedigree Charts
Start by identifying affected individuals and their relationships to deduce the inheritance pattern.
Identifying Patterns of Inheritance
Autosomal Recessive Traits
- Characteristics:
- Trait may skip generations.
- Unaffected parents can have affected children.
- Both males and females are equally affected.
- Genotypes:
- Affected individuals: aaaaaa (homozygous recessive).
- Carriers: AaAaAa (heterozygous, unaffected).
- Albinism is a recessive trait.
- Parents with normal pigmentation (carriers) can have a child with albinism.
Look for traits appearing in children of unaffected parents.
Autosomal Dominant Traits
- Characteristics:
- Trait appears in every generation.
- Affected individuals have at least one affected parent.
- Both males and females are equally affected.
- Genotypes:
- Affected individuals: AAAAAA or AaAaAa.
- Unaffected individuals: aaaaaa.
Huntington’s Disease follows a dominant inheritance pattern. Each child of an affected parent has a 50% chance of inheriting the trait.
