Saint Joseph Notre Dame High School 9

Overview of Pedigrees

  • Pedigrees are diagrams that track inheritance of specific traits through family generations, resembling family trees.

  • Focus trait example: widow's peak.

Basic Symbols and Structure

Gender Representation

  • Males: Squares

  • Females: Circles

Trait Representation

  • Shaded symbols indicate individuals expressing the trait; unshaded indicates those who do not.

Mating and Offspring

  • A line connects mating individuals.

  • Offspring are listed in order of birth.

Generation and Individual Labeling

  • Generations are numbered with Roman numerals (I, II, III, ...).

  • Individuals are numbered sequentially (1, 2, 3, ...) within each generation.

Inheritance Patterns

Recessive Disorders

  • Definition: Both alleles must be recessive for the trait to be expressed.

  • Heterozygous individuals appear normal but are carriers.

  • Example: Albinism (homozygous recessive).

    • Child must inherit both recessive alleles (aa) to exhibit the disorder.

Dominant Disorders

  • Definition: Only one dominant allele is needed to express the trait.

  • Heterozygous individuals are affected as are homozygous dominant individuals.

  • Example: Achondroplasia (dwarfism) and Huntington's disease.

    • Huntington's is a lethal dominant allele, manifesting in adulthood (30s-40s).

Types of Inheritance Patterns

Autosomal Dominant vs. Recessive

  • In autosomal dominant disorders, two affected parents cannot have an unaffected child.

  • In autosomal recessive disorders, two unaffected parents can have an affected child (if both are carriers).

X-Linked Dominant vs. Recessive

  • X-Linked Dominant: All daughters of an affected father will inherit the condition due to only having one X from their father.

  • X-Linked Recessive: All sons from an affected mother will be affected because they receive their one X from her, coupled with a Y from their father.

Lab Project Introduction

  • Tongue Curling: A genetic trait where the ability to curl the tongue is dominant.

    • Genotypes:

      • Individuals who can curl: TT or Tt

      • Individuals who cannot curl: tt

  • Students will create a pedigree for their own families based on this trait.

Pedigree Creation Instructions

  • Start with individuals who cannot curl their tongue to easily determine their genotype.

  • Use question marks for unsure genotypes. For example, a person who can curl their tongue but whose genotype is unknown can be labeled as T?.

  • Students are encouraged to collect data from both parents and siblings to construct their pedigree.

Lab Participation and Additional Resources

  • Each student must gather data from family members over two days to complete their pedigree.

  • A suggested online tool is Whimsical, but hand-drawn pedigrees are also accepted.

  • Minimum of 5 family members is required for the pedigree, but more is encouraged to enrich results.

Conclusion and Practice

  • Practice exercises will follow the pedigree lab to solidify understanding of pedigree analysis and inheritance patterns.