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?