In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F 1 are blue. When the blue F 1 plants are selfed, the F 2 plants occur in the ratio 9 blue : 3 pink : 4 white.
-How many gene pairs control the flower color phenotype?
A) 0
B) 1
C) 2
D) 3
E) 4

Question

In a certain species of plant, flowers occur in three colors: blue, pink, and white. A pure-breeding pink plant is mated with a pure-breeding white plant. All of the F 1 are blue. When the blue F 1 plants are selfed, the F 2 plants occur in the ratio 9 blue : 3 pink : 4 white. 
-How many gene pairs control the flower color phenotype?
A) 0
B) 1
C) 2
D) 3
E) 4

Quizplus · Accepted Answer

The 9:3:4 ratio suggests a dihybrid cross involving two gene pairs with epistasis, where one gene pair masks the expression of the other.

In a Certain Species of Plant, Flowers Occur in Three