Lecture Notes: Introduction to Genetics - Gregor Mendel

Gregor Mendel: The Father of Genetics

• Location: A quiet Monastery Garden in Austria
• Time Period: 1800s
• Noted for his curiosity about life and natural phenomena

Experiments with Pea Plants

• Focused on individual characteristics of pea plants:
  • Variations in height
  • Seed shape
  • Seed color
  • Flower color
• Conducted cross-pollination experiments:
  • Crossed tall plants with short plants
  • Crossed yellow peas with green peas
• Meticulous note-taking during observations

Generations of Pea Plants

• F1 Generation: Offspring from initial cross
  • Traits seemed to disappear (only tall or yellow peas)
  • Contrary to expectations of blending traits
• F2 Generation: Offspring from crossing F1 generation
  • Reappearance of hidden traits
  • Observed specific proportions:
    • 3 tall : 1 short
    • 3 yellow : 1 green

Fundamental Laws of Heredity

1. Law of Segregation

• Genes exist in multiple forms (alleles)
  • Example: Seed color alleles:
    • Yellow (Y) and Green (y)
• During gamete formation, alleles segregate
• Each gamete contains one allele for each trait
• At fertilization, two alleles combine for each gene

2. Law of Dominance

• Traits can be dominant or recessive
• Dominant alleles mask the expression of recessive alleles
  • Example: Purple flowers (dominant) vs. White flowers (recessive)
  • Plant with one purple and one white allele will have purple flowers

3. Law of Independent Assortment

• Different traits are inherited independently
• Analogy: Choosing an entree and dessert at a restaurant
• Example: Plant height does not affect seed color or flower color

Conclusion

• Mendel's findings laid the foundation for modern genetics
• Future topics will include:
  • Application of Mendel's laws to humans
  • Genetic disorders
  • Exceptions to Mendel's laws
• Speaker: Leslie Samuel from Interactive Biology
• Encouragement to continue exploring the complexities of genetics