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 / Male|
|Circle / Female|
|Diamond / Gender unknown|
|Line above / Siblings|
|Angled lines above / Twins|
|Line between / Partners|
|Two lines between / Consanguineous (blood related) couple|
|Line down / Children|
|Shaded / Affected individual|
|A small circle inside a larger circle or square / Carrier|
|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?
© St George’s, University of London