Law of Dominance Definition Biology

Learn about the law of dominance in biology and how it influences genetic inheritance. Explore real-world examples and the significance of this principle for breeding, medical research, and evolutionary studies.


The law of dominance is a principle in biology that explains the inheritance of traits from one generation to the next. This law states that one allele will be expressed over another when both are present in an organism’s genotype. In this article, we will explore the definition of the law of dominance, its significance in genetics, and real-world examples.

Understanding the Law of Dominance

According to Gregor Mendel, the father of modern genetics, each organism has two alleles for a particular trait, one inherited from each parent. When an organism has two different alleles for a trait, one will be dominant and the other recessive. The dominant allele will be expressed in the organism’s phenotype, while the recessive allele will be masked.

Significance in Genetics

The law of dominance is crucial in understanding how traits are passed down from parents to offspring. By studying dominant and recessive alleles, geneticists can predict the probability of certain traits appearing in future generations. This knowledge is valuable in breeding programs, medical research, and evolutionary studies.

Examples of the Law of Dominance

  • Eye color: In humans, brown eye color is dominant over blue. If a person inherits one allele for brown eyes and one for blue eyes, they will have brown eyes due to the dominance of the brown allele.
  • Seed shape in pea plants: Mendel’s famous experiments with pea plants demonstrated the law of dominance. He found that smooth seed shape was dominant over wrinkled seed shape, leading to predictable ratios in the offspring.

Case Studies

In a study of coat color in horses, researchers discovered that the gene for black coat color is dominant over the gene for chestnut coat color. By analyzing pedigrees and conducting genetic tests, breeders can produce desired coat colors in offspring.


The law of dominance is a fundamental concept in biology that explains how certain traits are expressed in organisms. By understanding this principle, scientists can unravel the complexity of genetic inheritance and make informed decisions in various fields. From eye color in humans to coat color in horses, the law of dominance plays a crucial role in shaping the world around us.

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