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PEDIGREES

PEDIGREES. A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. These diagrams make it easier to visualize relationships within families, particularly large extended families.

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PEDIGREES

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  1. PEDIGREES • A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. • These diagrams make it easier to visualize relationships within families, particularly large extended families. • Pedigrees are often used to determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases.

  2. Sample In a pedigree, squares=males and circles=females. Horizontal lines connecting a male and female represent mating. Vertical lines extending downward from a couple represent their children. Subsequent generations are therefore written underneath the parental generations and the oldest individuals are found at the top of the pedigree.

  3. Mode of Inheritance • Autosomal dominant: Autosomal dominant inheritance means that the gene carrying a mutation is located on one of the autosomes (chromosome pairs 1 through 22). This means that males and females are equally likely to inherit the mutation. "Dominant" means that having a mutation in just one of the two copies of a particular gene is all it takes for a person to have a trait.

  4. Autosomal Recessive: • the gene carrying the mutation is located on one of the autosomes(chromosome pairs 1 through 22). • This means that males and females are equally affected. "Recessive" means that both copies of the gene must have a mutation in order for a person to have the trait.

  5. X- linked: Males are more affected than females. • The key for determining if a dominant trait is X-linked or autosomal is to look at the offspring of the mating of an affected male and a normal female. • If the affected male has an affected son, then the disease is not X-linked. All of his daughters must also be affected if the disease is X-linked.

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