Question

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

(a) 1:2:1 and 3: 1 :1 (b) 3:1 and 1 :2:1 (c) 1:2:1 and 1:2:1 (d) 1:1 and 1:1:1.

Answer 1

Correct option (c) 1:2:1 and 1:2:1

Explanation:

Son.retimes two genes of the allelomorphic pair do not show a dominant-recessive relationship, but when presents together, they show intermediate trait or incomplete dominance. Incomplete dominance is not blending inheritance because parental characters reappear in F₂ generation. ln 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 pinks: 1 white-flowered plants with the phenotypic ratio being the same as a 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.