3.19 understand hwo to interpret family pedigrees

A pedigree diagram enables someone to easily show a specific gene within a family. Here's how they work...

- A square represents a male
- A circle represents a female
- Coloured in represents the person has that allele/characteristic
- Blank implies that the characteristic/allele is not present
- You may see half a square/circle coloured in. This implies the allele is present but recessive so the characteristic is not present.

NOTE: This is not always the case but most often is, in an exam situation there will be a key so you do not need to learn this.


For example, in this particular family, the mother carries a particular gene, which the sons have inherited. However, the father and daughters do not carry this gene...