Question

In a flower garden, a horticulturist is growing purple and white pansies. The horticulturist notices that a new pansy has sprouted. When it finally flowers, the pansy is lavender. With a botanist's help, an individual decides to cross the lavender pansy with the white pansy. Will this result in any purple pansies? Explain.

Answer 1

Incomplete dominance is a phenomenon in which the the blending of two alleles(for two different phenotypes) results in a third phenotype in the progeny, that is distinct from the phenotypes of both parents. An example of this is given in the question. A plant that has white flowers(phenotype 1) is crossed with a plant that has purple flowers(phenotype 2). The result, is a plant with lavender flowers(phenotype 3). Lavender is a shade that can be described as a mixture or a blend of white and purple.

Let the genotype of the white pansy be ww. Let the phenotype of the purple pansy be WW. When we cross the two plants, we obtain 4 genotypes, all heterozygous Ww. Ww is the genotype for the lavender pansy, where incomplete dominance is occuring, leading to the color lavender. When we cross the lavender plant with genotype Ww and the white plant with genotype ww, we obtain 4 genotypes, 2 Ww(heterozygous, displaying incompete dominance leading to lavender), and 2 ww(homozygous white). There is an absence of the homozygous WW genotype.This means that when we cross the lavender pansy with a white pansy, we obtain NO purple pansies.

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