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  4. When red and white flowered Mirabilis plants are crossed all pink flowers are seen in F1 generation. When F1 progeny is selfed, the expected phenotypic and genotypic ratios are

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Q. When red and white flowered Mirabilis plants are crossed all pink flowers are seen in F1 generation. When F1 progeny is selfed, the expected phenotypic and genotypic ratios are

AIIMSAIIMS 2018Principles of Inheritance and Variation

Solution:

Sometimes two genes of allelomorphic pair do not show dominant-recessive relationship, but when present together, they show intermediate trait or incomplete dominance. Incomplete dominance is not blending inheritance because parental characters reappear in F2 generation. In Mirabilis jalapa, there are two types of pure breeding plants, red flowered and white flowered. On crossing them the F1 plants or hybrids possess pink flowers. On selfing them, F2 generation has plants in the ratio of 1 red : 2 pink : 1 white flowered plants with phenotypic ratio being same as genotypic ratio.
Genotypic ratio = 1RR : 2Rr : 1rr
Phenotypic ratio = 1 Red : 2 Pink : 1 White
Both genotypic ratio and phenotypic ratio are same, i.e., 1 : 2 : 1.

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