From Seed to Seed:
Plant Science for K-8 Educators

Incomplete Dominance

Up until now, we have been using examples of traits that have distinct dominant and recessive expressions. In some cases, however, a gene can have two or more different expressions, none of which is dominant over the others. This is called incomplete dominance. Let's briefly look at one example.

In addition to peas, Mendel also experimented with snapdragon plants. He showed that by crossing a white-flowered snapdragon with a red-flowered snapdragon, he could produce a plant with pink flowers. In other words, the two expressions blended, forming the color pink.

Many traits exhibit incomplete dominance. And some traits, such as hair color, are dependent upon not just one pair, but rather several pairs of genes.