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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. We have also included a PDF version of the table in the downloads section below.

Please note: This table is best viewed in landscape mode when viewing this step on a mobile device.

Symbol Description / Meaning
Square Symbol Square / Male
Circle Symbol Circle / Female
Diamond Symbol Diamond / Gender unknown
Line Above Symbol Line above / Siblings
Angled Lines Above Symbol Angled lines above / Twins
Line Between Symbol Line between / Partners
Two Lines Between Symbol Two lines between / Consanguineous (blood related) couple
Line Down Symbol Line down / Children
Shaded Symbol Shaded / Affected individual
Shaded Dot Symbol A small circle inside a larger circle or square / Carrier
Line Diagonally Through Symbol Line diagonally through symbol / Individual is deceased

Just for fun

Try drawing your own family pedigree. If you can, go back three generations (including your own). Is your family pedigree straightforward or, like many families, more complex and challenging to draw?

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This article is from the free online course:

The Genomics Era: the Future of Genetics in Medicine

St George's, University of London

Get a taste of this course

Find out what this course is like by previewing some of the course steps before you join:

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    In this video, Lead Educator, Dr Kate Tatton-Brown welcomes learners to the course and explains the course aims and outcomes.

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    This video describes how structural chromosome abnormalities occur when errors occur in recombination.

  • Responsibility in the genomic era
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    In this tutorial, you will hear from Dr Carwyn Rhys Hooper on the concept of responsibility for health.

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