How is a family tree drawn?

Wellcome Connecting Science | Graphic | Empowering People: Genetic Counselling in Focus

Although they share similar details, pedigrees are different to family trees that you might compile when tracing your family’s genealogy. For your genealogical story you might be interested in relatives going back many generations, or identifying distant cousins, but a genetic counsellor usually takes a three-generation family tree and uses this to work out whether there are clear disease inheritance patterns showing in the family.

In the clinic the family members of interest are the ones you are most closely related to, so most family trees only go back as far as your grandparents and will capture details of your parents, your siblings, your children and your parents’ siblings. This is because you are more genetically similar to these individuals, meaning that an alteration that is present in your DNA may be present in theirs, and vice versa.