BRAINCAKEPedigree Diagrams
A pedigree diagram (family tree) shows how a characteristic is inherited through several generations of a family. It is used to work out whether an allele is dominant or recessive, whether it is sex-linked, and the genotypes of family members.
Standard symbols:
• square = male, circle = female
• shaded symbol = affected by the condition, unshaded = unaffected
• a horizontal line joining a male and female = parents
• a vertical line down to a horizontal line of symbols = their children
• generations are labelled with Roman numerals (I, II, III) and individuals with numbers
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More in Genetic Information
- Gene Linkage
- Identifying Linked Genes
- Chromosome Mapping
- Sex-Linkage
- The Albino Trait
- Sex-Linked Diseases
- Red-Green Colour Blindness
- Haemophilia
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics