Mendel's Laws

Key Notes on Mendel’s Rediscovery and Genetic Terminology

Rediscovery of Mendel’s Work (1900)

• Mendel’s research was largely ignored after its publication in 1866.

• His work was rediscovered in 1900 by Hugo De Vries, Carl Correns, and Erich Von Tschermak-Seysenegg, who independently reached the same conclusions.

• Once genes and alleles were discovered, scientists could restate Mendel’s laws in genetic terms.

• This led to the development of modern genetics.

Genetic Terminology

Mendel’s Laws in Genetic Terms

1. Law of Segregation:

   • Explanation: Each organism has two alleles per gene, which separate during meiosis so each gamete gets one allele.

   • Genetic Basis: This occurs when homologous chromosomes separate during gamete formation.

2. Law of Independent Assortment:

   • Explanation: Genes for different traits assort independently during meiosis.

   • Genetic Basis: This happens because genes on different chromosomes separate independently during meiosis.

Genotype vs. Phenotype

• Genotype = The genetic makeup (PP, Pp, pp).

• Phenotype = The physical trait (purple or white flowers).

• One phenotype can result from different genotypes:

  • PP (homozygous dominant) → Purple

  • Pp (heterozygous) → Purple (because P is dominant)

  • pp (homozygous recessive) → White

Impact on Darwin’s Theory of Evolution

• If Darwin had known about Mendel’s work, he would have understood how traits are inherited, strengthening his argument for natural selection.

• This could have made his theory more widely accepted sooner.