Family Pedigrees (Edexcel IGCSE Biology): Revision Note

Family Pedigrees

• Family pedigree diagrams are usually used to trace the pattern of inheritance of a specific characteristic (usually a disease) through generations of a family

• This can be used to work out the probability that someone in the family will inherit the genetic disorder

Interpreting a family pedigrees

• Males are indicated by the square shape and females are represented by circles

• Affected individuals are red and unaffected are blue

• Horizontal lines between males and females show that they have produced children (which are shown underneath each couple)

• The family pedigree below shows:

  • both males and females are affected

  • every generation has affected individuals

  • one family group that has no affected parents or children

  • the other two families have one affected parent and affected children as well

A family pedigree chart