Breeding garden pea plants (Pisum sativum), which can self-fertilize or cross-fertilize.

Breeding garden pea plants (Pisum sativum), which can self-fertilize or cross-fertilize.

Garden pea flower, cut in half. Male gametes form in pollen grains produced by anthers, and female gametes form in carpels. Experimenters can control the transfer of hereditary material from one flower to another by snipping off a flower’s anthers (to prevent the flower from self-fertilizing), and then brushing pollen from another flower onto its carpel.

In this example, pollen from a plant that has purple flowers is brushed onto the carpel of a  white-flowered plant.

Later, seeds develop inside pods of the cross-fertilized plant. An embryo in each seed develops into a mature pea plant.

Every plant that arises from the cross has purple flowers. Predictable patterns such as this are evidence of how inheritance works.