Pedigree Charts: Tracing Traits

Introduction

• Pedigree charts assist scientists in tracing the inheritance of traits.
• Represents family relationships and the passage of genetic traits using symbols.

Basic Representation

• Squares: Males
• Circles: Females

Family Example

• Couple: Brown-haired male and blond-haired female.
• Children:
  • Firstborn: Blond-haired son
  • Secondborn: Brown-haired female
• Daughter's Family:
  • Daughter marries a brown-haired male.
  • Children: Blond-haired female and brown-haired female.

Pedigree Chart Details

• Trait Focus: Hair color.
  • Brown hair: Dominant trait
  • Blonde hair: Recessive trait
• Genotypes:
  • Male: Heterozygous (Bb) – Half-shaded square
  • Wife: Homozygous recessive (bb) – Fully shaded circle
  • Son & Daughter: Reflect offspring traits
    • Son: Blonde hair (bb) – Fully shaded square
    • Daughter (Bb) – Half-shaded circle

In-Law and Offspring

• Son-in-law: Heterozygous (Bb) – Half-shaded square
• Daughter’s Children:
  • Firstborn (female): Blonde hair (bb) – Fully shaded circle
  • Secondborn (female): Two dominant genes (BB) – Unshaded circle

Key Concepts

• Carrier: Individual with one dominant and one recessive gene (e.g., Bb)
  • Represented by a half-shaded symbol.
• Fully Shaded: Represents an individual displaying the recessive trait.
• Unshaded: Represents dominant trait without carrying recessive.

Conclusion

• Pedigree charts are useful tools for visualizing genetic inheritance.
• They simplify complex family trees, focusing on specific traits like hair color.
• Encourage thinking like a scientist to analyze family traits through pedigree charts.