Question

Suppose you have a plant with petals that are normally blue. Suddenly you see some white-petaled plants. Cross 1: You cross the white with the blue and you get all an F1 population that is all blue. In the F2 generation you see a ratio of 101:33 blue to white-petaled plants. Another line of flowers shows pink petals. Cross 2: You cross the pink with the blue and once again the F1 generation shows all plants with blue petals. However, in the F2 generation the ratio is 192:63 blue to pink-petaled plants. Cross 3: You cross the pink and the white. You get all blue in the F1 generation. Cross 4: You cross the F1 individuals obtained from cross 3 and the F2 generation shows a segregation of 272:121:89, blue to white to pink-petaled plants. Which of the crosses above represent an example of complementation. Check all that apply.

  

Cross 1

Cross 2

Cross 3

Cross 4

Answer 1

Cross 3 and Cross 4 are the examples of complementation.

Cross 1 and Cross 2 are example of ideal monohybrid cross of dominant recessive type . where ration of F₂ is 3:1 in both cross 1 and cross 2. In F1 one trait is completely dominant over the other.

In cross 3, Neither pink, nor white appear in the F1, on the contary, blue coloured petal containing plats are obtained which is due to the complementation.

In cross 4, when Blue coloured petal containing plants, obtained in F₁ of cross 3, are crossed, blue, white and pink coloured petal containing plants are observed n F₂. Here also blue coloured petals are obtained due to complementation between pink and white colour.