Gregor Mendel's Pea Experiment

Gregor Mendel was frustrated. He'd studied the work of other plant hybridizers closely, but their observations were general and their conclusions fuzzy. Mendel had noticed regular patterns in the hybrid flowers he grew. He decided to track traits across generations. He chose the garden pea for his experiments because it had clearly defined traits. He focused on seven contrasting pairs of traits and crossed plants that differed for each trait. To create hybrids, Mendel cross-fertilized parent plants by hand. When his first crop of hybrids grew, they exhibited the characteristics of only one parent. Mendel called this trait the dominant one. The other trait had disappeared, but not forever. When Mendel left these plants to fertilize themselves, the hidden trait returned in the next generation, outnumbered three to one by the dominant trait. Mendel called this trait recessive. Mendel realized that whatever was governing the recessive traits was still there in the first hybrids, deep down in their cells, and had been transmitted to the second generation. Mendel let these hybrids self-fertilize too. In their offspring and in later generations, a pattern emerged. Mendel did the math and concluded that whatever determined the traits—he called them elements, we call them genes—were present in the parents in pairs, but split during reproduction, passing to the offspring in a predictable way. Mendel went on to cross peas that differed in more than one trait. The first generation plants were all the same, all dominant traits, but the second had every possible combination of traits, again in regular patterns. Mendel concluded that the elements governing those traits were not passed on together. Mendel conducted these experiments over multiple generations, patiently growing plants, counting peas, and recording patterns for eight years. you