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*Biology Name ___________________________
Date________________ Period_______
STUDYING PEDIGREES ACTIVITY
Introduction: A pedigree is a visual chart that depicts a family history or the transmission of a specific trait.
They can be interesting to view and can be important tools in determining patterns of inheritance of specific
traits. Pedigrees are used primarily by genetic counselors when helping couples decide to have children when
there is evidence of a genetically inherited disorder in one or both families. They are also used when trying to
determine the predisposition of someone to carry a hereditary disease for example, familial breast cancer.
The Components of a Pedigree:
Squares are used to indicate males in a family.
Circles are used to indicate females.
If the individual is “affected" by the trait (dominant or recessive) we darken the shape.
A line between a male and a female indicates a marriage or union.
A line drawn down from the marriage line indicates offspring.
Sometimes, you will see some shapes filled in only half way -
this notation indicates a hybrid (heterozygous) or carrier of the trait.
Read pages 396-397 (Sect. 14.1) in your textbook for more information.
