Gregor Mendel experimented with pea plants for seven years in a small garden in a monastary near Brno, Czechoslovakia in the Austrian Alps. During those seven years he worked with plants that had certain traits that came and went in predictable ways. In many cases he noted tall or short plants but no medium size plants, for example. When he crossbred a tall plant with a short one, he always got a tall plant. But those "tall" seeds from these plants produced a few short plants in the next generation. The experiments led to dramatic insights into how genetics worked. This module will help you understand some of the basic principles that we believe govern the blueprints for life.
Mendel worked with traits such as color, stem length, and nature of the seed. As he performed his experiments, he recognized "weaker" traits and "stronger" ones. He named the stong traits DOMINANT and the weaker one RECESSIVE . In order to conceptualize this relationship, explore this brief explanation of what Mendel did.
First Generation:Mendel began by producing a series of true-breeding pea plants. This meant that he was sure he had only traits for yellow or green when he began to crossbreed plants. In the first cross, Mendel saw only the "strong" trait for green color. There was no direct evidence that the yellow trait existed.
Second Generation:In the cross of the plants into the second phase (generation), Mendel discovered that he had about 3 green plants to every 1 yellow plant. The green trait had to have been present in the earlier parent plant and uneffected by the pairing with the "stronger" trait. The "stronger" trait had expressed itself in appearance, but the "weaker" trait had been present . Otherwise it could not have reappeared in the second crossing.
