Genetics Summary

Introduction to Genetics

• Genetics: The scientific study of heredity

Key Vocabulary

• Trait: Specific characteristic differing among individuals (e.g., eye color)
• Gene: DNA segment determining a trait; located on chromosomes (e.g., gene for eye color)
• Hybrid: Offspring of parents with different traits
• Gametes: Reproductive cells (sperm & egg)
• Allele: Variation form of a gene (represented by letters)
• Homozygous: Same alleles (e.g., WW or ww)
• Heterozygous: Different alleles (e.g., Ww)
• Genotype: Actual allele combination (e.g., WW, Ww, ww)
• Phenotype: Observable trait (e.g., Widow’s Peak)

Gregor Mendel

• Father of genetics; conducted experiments in the mid-1800s with pea plants.
• Key Conclusions:
  1. Inheritance determined by factors from generation to generation
  2. Principle of Dominance: Some alleles are dominant, others recessive.
  3. Segregation: Each gamete carries one allele for each gene.
  4. Independent Assortment: Genes for different traits segregate independently.

Punnett Squares

• Tool to predict offspring genotypes based on parents' genotypes.
• Diagrammatic representation of genetic crosses.

Patterns of Inheritance

• Incomplete Dominance: Heterozygous phenotype (e.g., pink flowers) is blended.
• Codominance: Both alleles expressed (e.g., roan cattle).
• Multiple Alleles: More than two allele choices (e.g., ABO blood system).
• Polygenic Traits: Traits controlled by multiple genes (e.g., skin color).