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Biology · Glossary

What is Pedigree?

Definition 16.4 High School Biology · Chapter 16 — Genetic Variation and Disease

A pedigree is a diagram of a family over several generations: squares for males, circles for females, a horizontal line joining a couple, a vertical line down to their children, filled symbols for affected people. Generations are numbered I, II, III from the top; individuals are numbered from the left.

A pedigree for cystic fibrosis. II-2 and III-2 are affected; their parents are healthy. Both couples I-1/I-2 and II-3/II-4 must be carriers; II-3, healthy brother of an affected child, is a carrier with probability 2/3.
A pedigree for cystic fibrosis. II-2 and III-2 are affected; their parents are healthy. Both couples I-1/I-2 and II-3/II-4 must be carriers; II-3, healthy brother of an affected child, is a carrier with probability 2/32/3.
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