1. Introduction to Inheritance

  • Inheritance is the transmission of genetic traits from parents to offspring.
  • It follows the principles established by Gregor Mendel, known as the Father of Genetics.
  • Genetic traits are controlled by genes located on chromosomes.
  • Each gene has different forms called alleles, which determine variations in traits.

2. Mendelian Laws of Inheritance

  • Mendel conducted experiments on pea plants (Pisum sativum) and formulated three laws.
  • Law of Dominance: In a heterozygous condition, one allele is dominant, while the other is recessive.
  • Law of Segregation: During gamete formation, allele pairs separate so that each gamete carries only one allele.
  • Law of Independent Assortment: Genes for different traits assort independently during gamete formation.

3. Monohybrid Cross

  • A monohybrid cross studies the inheritance of a single trait.
  • Mendel crossed tall (TT) and dwarf (tt) pea plants.
  • The F1 generation had all tall plants (Tt) due to dominance.
  • The F2 generation (self-crossed) showed a 3:1 phenotypic ratio (tall: dwarf).
  • Genotypic ratio was 1:2:1 (TT:Tt:tt).

4. Dihybrid Cross

  • A dihybrid cross studies the inheritance of two traits simultaneously.
  • Mendel crossed plants with yellow round seeds (YYRR) and green wrinkled seeds (yyrr).
  • The F1 generation had all yellow round seeds (YyRr).
  • The F2 generation showed a 9:3:3:1 phenotypic ratio:
    • 9 Yellow Round
    • 3 Yellow Wrinkled
    • 3 Green Round
    • 1 Green Wrinkled

5. Key Terminologies in Mendelian Genetics

  • Gene: A unit of inheritance.
  • Allele: Different forms of a gene.
  • Homozygous: Having identical alleles (TT or tt).
  • Heterozygous: Having different alleles (Tt).
  • Genotype: Genetic makeup of an organism.
  • Phenotype: Physical expression of a trait.
  • Dominant Trait: Expressed in heterozygous condition.
  • Recessive Trait: Expressed only in homozygous condition.

6. Applications of Mendelian Genetics

  • Helps in plant and animal breeding to develop improved varieties.
  • Used in genetic counseling to predict inherited disorders.
  • Forms the basis for modern genetics and biotechnology.

7. Conclusion

  • Mendel's experiments laid the foundation for classical genetics.
  • His laws explain how traits are inherited across generations.
  • Understanding inheritance helps in medical, agricultural, and genetic research.

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