Mendelian Genetics Lecture Notes

Introduction to Genetics

• Concept of Heredity
  • Traits are passed on from generation to generation.
  • Gregor Mendel: Pioneer in understanding genetics.
• Historical Perspective
  • Blending hypothesis was initially believed.
  • Mendel proposed discrete units of inheritance (genes).

Gregor Mendel's Background

• Entered Augustinian monastery; studied science in Vienna.
• Worked with pea plants to explore heredity.

Mendel's Experiments with Pea Plants

• Why Pea Plants?
  • Visible traits like flower color, seed shape, pod color.
  • Short generations, easy to gather data.
  • Controlled mating by removing stamens.
• Hybridization Process
  • True-breeding plants used.
  • Parental generation (P), F1 generation (first filial), F2 generation (second filial).

Mendel's Laws of Inheritance

• Law of Segregation

  • F1 generation all purple (dominant) when purple and white are hybridized.
  • F2 generation shows a 3:1 purple to white ratio.
  • Dominant (purple) vs. recessive (white) traits.
  • Explained using Punnett squares.

• Law of Independent Assortment

  • Dihybrid crosses (two traits at once).
  • F1 heterozygous for both traits; F2 generation shows 9:3:3:1 ratio.
  • Traits determined individually and separated randomly.

Advanced Concepts in Genetics

• Degrees of Dominance
  • Complete Dominance: Dominant allele always expressed.
  • Incomplete Dominance: Intermediate phenotype (e.g., pink snapdragons).
  • Co-dominance: Both phenotypes expressed (not covered in detail).

Conclusion

• Mendel's experiments foundational for genetics despite limitations.
• Extended Mendelian genetics helps explain complex inheritance patterns.

Additional Resources

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