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.

1. (a)(i)Define the term allele.[2]
2. (a)(ii)Suggest ways in which the expression of allele R allows pigment production.[3]
3. (b)Complete Fig. 3.2 to show the results of a cross between two I. purpurea plants that are heterozygous at both loci. parental genotypes: parental gametes: results of cross: • show parental gametes in first column and top row • show offspring genotypes and phenotypes in square boxes phenotypic ratios: [Figure 3.2][5]

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