Mendel's research revealed that white flowers are a recessive trait in pea plants.
Throughout history, scholars proposed ideas about inheritance after making the observation that offspring often resembled the parent. In the 19th century, the dominant hypothesis proposed that genetic material "blended," creating an intermediary between the two parents. For example, a large dog and a small dog should produce puppies that grow to be midsized between the two parents. However, observations made by Charles Darwin showed that blending couldn't account for heredity in many cases.
The eventual answer to the question of heredity was discovered by an Austrian monk, Gregor Mendel, who founded the modern science of genetics after a series of experiments explaining heredity in pea plants. Today, you can easily replicate these experiments, including determining the genotype -- the genetic makeup -- of individual plants. Homozygous plants contain two genes of the same type: two dominant genes or two recessive. Heterozygous plants contain one of each, and the plant displays the dominant trait.
Instructions
1. Select which traits to study. Mendel studied several traits where you can easily observe the genotype of the plant through self-pollination, including seed shape, seed color, pod shape, pod color, plant size, flower color and flower position. Each of these traits acts independently from the others, meaning that a plant that is homozygous with respect to flower color might be heterozygous with respect to seed shape.
2. Allowing bees to access your pea plants will ruin your results.
Plant pea seeds according to the instructions on the seed packet and provide the care needed for the plant to grow. When the plant begins producing flowers, cover the flowers or enclose the plant inside of a screen. This prevents insects from carrying pollen into the flower from other pea plants.
3. Observe and note the characteristics that Mendel studied. Identify which characteristics are genetically dominant and which are recessive. If you observe recessive characteristics -- wrinkled seeds, green seeds, white flowers or small plants -- you know that the plant is homozygous recessive for that trait.
4. Allow the plant to self-pollinate and produce seeds. Pea plants self-pollinate easily, so you do not have to help the plant along in any way. Plant the resulting seeds and observe the characteristics of the offspring. Homozygous dominant plants will produce offspring that all share the same characteristic. For example, a pea plant that is homozygous dominant with respect to plant height will produce only tall offspring, barring the occasional and rare mutation. The offspring of heterozygous plants show a mixture of the two traits in roughly a three-to-one ratio. For example, a heterozygous plant would produce approximately three tall offspring for every one short offspring.
