One of the greatest mysteries – how we inherit traits from our parents – was solved in the 1800s by the Austrian monk Gregor Mendel. Although he published his work in 1866, it went almost entirely unrecognized until the 1900s, long after his death.
Mendel worked with pea plants, carefully characterizing their traits and cross-breeding them over many generations. He observed that many traits occur in only two different forms (short or long stems, purple or white flowers, round or wrinkled seeds). When a short plant is crossed with a tall plant, the offspring are all either tall or short, not of middle stem length. This observation countered the “blending theory” that was generally accepted at the time.
Mendels peasHe established many pure-breeding lines – for instance short plants that when cross-bred always had short offspring and tall plants that always had tall offspring. Interestingly, when a pure-bred short plant is crossed with a pure-bred tall plant, the first offspring (f1 generation) are all tall! If these tall f1 plants are cross-bred to one another, the next generation (f2) consistently have a 3:1 ratio of tall to short plants.
With these ratios and careful breeding experiments, Mendel discovered the basic laws of inheritance. He came to several conclusions: