Question

In Mirabilis jalapa, RR, Rr and rr determine red, pink and white colours respectively. When $F_1$ hybrid of RR and rr was crossed with dominant parent, the ratio produced is

• A. All red
• B. 2 Red : 2 Pink
• C. All white
• D. 2 Pink : 2 white

Answer 1

Answer: (B)

2 Red : 2 Pink

In Mirabilis jalapa, flower colour shows incomplete dominance. The F1 plant obtained by the crossing of pure Red flowered plant(RR) with pure white flowered plant(rr) shows pink flowers(Rr). This F1 plant(Rr) is crossed is with pure red flowered plant(RR), in the next generation 2 plants with red flowers and 2 plants with pink flowers are formed. The ratio is 2:2 = 1:1

So, the correct option is ‘2 red : 2 pink’.