Inheritance of two Traits / Dihybrid cross | Mende Law of independent Assortment | Genetics

Scientific Concepts

• Mendel's Laws:
  • Law of Segregation: Alleles separate during gamete formation, leading to the inheritance of traits.
  • Law of Independent Assortment: Different traits are inherited independently of one another.
• Alleles:
  • Dominant Alleles (represented by capital letters) mask the expression of recessive Alleles (represented by lowercase letters).
• Dihybrid Cross:
  • A genetic cross that examines the inheritance of two different traits simultaneously.

Methodology

1. Selection of Traits:
   • Mendel selected two traits to study: seed shape (round vs. wrinkled) and seed color (yellow vs. green).
   • Round shape (R) and yellow color (A) are dominant traits, while wrinkled shape (r) and green color (a) are recessive traits.
2. True Breeding Plants:
   • Mendel used true-breeding plants for both dominant and recessive traits to ensure consistent results.
3. Gamete Formation:
   • During gamete formation, Alleles segregate so that each gamete carries only one allele for each trait.
4. F1 Generation:
   • The first filial generation (F1) is produced by crossing dominant and recessive true-breeding plants, resulting in all round yellow seeds (RrAa).
5. F2 Generation:
   • F1 plants are self-fertilized to produce the second filial generation (F2), revealing the phenotypic ratios and confirming independent assortment:
   • Phenotypic ratio observed: 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green.

Findings

The results of Mendel's experiments demonstrated that Alleles for different traits assort independently during gamete formation, leading to new combinations in the offspring that were not present in the parental generation.

Researchers/Sources Featured

• Gregor Mendel (referred to as "Mandal" in the subtitles).