Flowers of the common morning-glory plant, Ipomoea purpurea, can have several different phenotypes. An example of these flowers is shown in Fig. 3.1. [Figure 3.1] Flower colour in I. purpurea is controlled by two genes on different chromosomes. Gene R/r, which codes for a protein involved in pigment production, has 2 alleles: • the dominant allele, R, allows pigment production : the recessive allele, r, prevents pigment production of any colour, resulting in white flowers. Gene T/t, which determines the type of pigment produced, has two alleles: : the dominant allele, T, results in purple flowers the recessive allele, t, results in red flowers.