Gregor Mendel selectively allowed pea plants to cross-pollinate and then observed the pea plants for seven different physical traits. He recorded the results of each pollination and made several important conclusions about the inheritance of traits based upon his experiments with the plants.
Based upon data resulting from the cross-pollination of two differing purebred pea plants, Mendel came to the conclusion that one instruction is inherited from each parent for a trait. These two inherited instructions can be the same, or they can be different. If the instructions are different, one trait is dominant over the other and is expressed in the physical characteristic of the offspring. Though one instruction may not be expressed, it still has the opportunity to be passed on to offspring.
Mendel completed his experiments as a Central European monk who lived in the mid-1800s. He published his ideas in 1866, many years before the invention of the microscope made observations of cellular processes possible. His conclusions about the inheritance of traits were contrary to the commonly accepted theories of inheritance at the time. Most believed inheritance was a result of a blending of the traits of the parents. His ideas were not commonly accepted until after his death.