mendel

Mendel's Laws of Inheritance

Introduction

• Gregor Mendel's foundational experiments on inheritance are critical for understanding genetic principles.

Key Experiments

• Mendel conducted two primary experiments to establish the laws of inheritance:

  • Monohybrid Cross

  • Dihybrid Cross

Monohybrid Cross

• Definition: A monohybrid cross involves breeding two individuals with homozygous genotypes that exhibit opposite phenotypes for a specific trait.

• Experiment Details:

  • Mendel crossed pea plants with opposing traits (tall and short).

  • First generation (F1) offspring were all tall (dominant trait).

  • F2 generation resulted in a phenotypic ratio of 3 tall to 1 short.

Dihybrid Cross

• Definition: A dihybrid cross involves two genes that differ in two observed traits.

• Experiment Details:

  • Mendel crossed plants with wrinkled-green seeds with those having round-yellow seeds.

  • All F1 progeny were round-yellow, indicating dominance of these traits.

Laws of Inheritance

• Law of Dominance (Mendel's First Law):

  • Hybrid offspring express only the dominant trait in their phenotype.

  • Recessive traits are those that are suppressed in the presence of dominant traits.

• Law of Independent Assortment (Mendel's Second Law):

  • Traits segregate independently during gamete formation.

  • Each hereditary factor assort independently, allowing various combinations of traits.

• Law of Segregation (Mendel's Third Law):

  • During gamete formation, two copies of each hereditary factor segregate.

  • Offspring receive one factor from each parent; alleles pair up randomly during fertilization.