Gregor Mendel: Planting the Seeds of Genetics

What Mendel Discovered

Mendel’s mathematical mind allowed him to “see” hidden patterns of heredity.

Earlier scientists had noticed the disappearance and reappearance of traits in hybrid plants. What Mendel did differently was count. And count. And count. Mendel used mathematics to draw conclusions about what was happening deep inside the cell.

Mendel concluded that every trait must be controlled by two “elements” (what we now call genes) that are present in every pea plant. As part of sexual reproduction, these elements separate and only one is passed down to the offspring. Whether a plant has green or yellow peas depends on the combination of elements that it received from its parents. If a plant receives two dominant elements, its trait will be dominant (i.e. yellow peas). If it receives two recessive elements, its trait will be recessive (i.e. green peas). If it receives one of each element, the dominant trait will mask the recessive trait. This is what caused all the green peas to disappear in Mendel’s first generation of plants.

Mendel went on to cross plants that differed in more than one trait—round-yellow peas with wrinkled-green ones, or tall, violet-blossomed plants with short, white-blossomed ones. As in his initial experiments, the traits appeared in predictable ratios. This told Mendel that the elements governing traits were not linked, but passed separately to the offspring.

Mendel’s results were published in a local scientific journal in 1866, but other scientists did not understand the importance of his work for several decades.

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