Genetics is the study of how traits pass from one generation to the next, and at its foundation lie the laws of heredity first described by Gregor Mendel in the mid-19th century. Working with pea plants in his monastery garden, Mendel uncovered simple rules that explain how characteristics such as flower color, seed shape, and plant height are inherited. These principles remain central to our understanding of biology today.
Law of Segregation
Mendel’s first law states that each individual carries two “factors” (now known as genes) for each trait, one inherited from each parent. During the formation of eggs and sperm, these paired factors separate, so each gamete carries only one factor for each trait. When fertilization occurs, offspring receive one factor from each parent, restoring the pair. This explains why a recessive trait (such as white flower color) can skip a generation and then reappear.
Law of Dominance
Mendel observed that when two different factors for a trait are present, one factor may mask the effect of the other. He called the visible factor the dominant trait and the hidden one the recessive trait. For example, in pea plants, the gene for purple flowers dominates the gene for white flowers, so a plant carrying one purple gene and one white gene will display purple blossoms.
Law of Independent Assortment
Mendel’s second major discovery is that genes for different traits are inherited independently of one another. During gamete formation, the separation of one pair of factors does not influence how another pair separates. In other words, the inheritance of seed color doesn’t affect the inheritance of seed shape. This law holds true when the genes in question reside on different chromosomes or are far apart on the same chromosome.
Together, these three Mendelian laws laid the groundwork for modern genetics. They allow scientists to predict how traits may appear in offspring, explain why siblings can look different, and serve as the starting point for more complex models of inheritance. Although we now know that some traits are influenced by multiple genes or by environmental factors, Mendel’s principles still apply to many simple inheritance patterns.
The legacy of Mendel’s work extends far beyond pea plants. Today, plant and animal breeders use these same laws to develop new varieties, while medical researchers apply them to understand genetic diseases. Even advanced fields like genetic engineering and genomics build on Mendel’s insights, demonstrating how a few simple rules can unlock the secrets of life itself.