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

Family pedigree chart, IGCSE & GCSE Biology revision notes

A family pedigree chart

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.