Inheritance of flower colour and flower position in pea plants are controlled by two genes. • Gene P/p controls flower colour. Allele P for purple flowers is dominant to allele p for white flowers. • Gene A/a controls flower position. Allele A for flowers growing from the side of the shoot (axial position) is dominant to allele a for flowers growing at the end of the shoot (terminal position), as shown in Fig. 2.1. [Figure 2.1] A biologist predicted that, if the genes are on different chromosomes, the ratio of the phenotypes of the F2 generation would be 9:3:3:1. The biologist carried out a breeding experiment. • Plants homozygous for white flowers and axial position were crossed with plants homozygous for purple flowers and axial position. • All the F1 plants had purple, axial flowers. • The F1 plants were crossed with each other. Table 2.1 shows the results for the F2 generation. Table 2.1 F2 phenotype frequency purple, axial flowers 1756 purple, terminal flowers 653 white, axial flowers 702 white, terminal flowers 234 total 3345