These determinants are called genes. Each parent has a gene pair in each cell for each trait studied. The F 1 from a cross of two pure lines contains one allele for the dominant phenotype and one for the recessive phenotype. These two alleles comprise the gene pair. One member of the gene pair segregates into a gamete, thus each gamete only carries one member of the gene pair.
Gametes unite at random and irrespective of the other gene pairs involved.
This can be depicted graphically in a Punnett square. From these results Mendel coined several other terms and formulated his first law. First the Punnett Square is shown. The Punnett Square allows us to determine specific genetic ratios. To test this hypothesis, Mendel selfed the F 2 plants.