In the context of a genetic analysis, a cross refers to the deliberate mating of two parental types of an organism to produce offspring whose phenotype will be studied. Gregor Mendel (1823-1884), who pioneered the discipline of genetics, usually used the German term Befruchtung (fertilization), which was later translated by William Bateson (1861-1926) as the term crossing.

Mendel's experiments involved crosses in pea plants (Pisum sativum). He united the pollen from the male reproductive structures, the anthers, of one plant with the stigma, that portion of the female part of the flower that receives the pollen, of another. Pea plants can be either cross-pollinated (i.e., the pollen of one plant fertilizing the ova of a second pea plant) or self-pollinated (i.e., the pollen of a plant fertilizing its own ova). Mendel was primarily interested in cases where the two plants being crossed...