Understanding a pedigree
Doctors can use a pedigree to show how genetic disorders are inherited in a family. They can use this to work out the probability that someone in a family will inherit a condition.
In order to understand the following presentations on inheritance patterns, you may find it useful to spend a few moments looking at the images below and familiarising yourselves with the meanings of the symbols and connecting lines used to draw pedigrees.
Please note - this table is best viewed in landscape mode when viewing this step on a mobile device.
Symbol | Description | Meaning |
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Square | Male |
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Circle | Female |
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Diamond | Gender unknown |
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Line above | Siblings |
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Angled lines above | Twins |
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Line between | Partners |
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Two lines between | Consanguineous couple |
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Line down | Children |
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Shaded | Affected individual |
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A small circle inside a larger circle/square | Carrier |
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Line diagonally through symbol | Individual is deceased |
Once you have seen some examples, you may wish to draw your own family pedigree and see the results.
© St George’s, University of London