Flower colour inheritance...?

Question

When the mechanism of flower colour inheritance in peas was investigated, red flowered plants were crossed with white flowered plants. The first generation all had red flowers. However, when these red flowered plants were allowed to self fertilize, about 25% of the offspring had white flowers, the remainder of the offspring having red flowers. In a similar investigation with the snapdragon plants, the red flowered plants were crossed with white flowers, the resulting first generation (F1) all had pink flowers. When these pink flowers self fertilized (the F2) about 25% of the offspring had white flowers, 25% had red flowers and about 50% had pink flowers.

Why are the results for peas different from those of the snapdragons?

Answer 1

Pea plants have traditional dominant/recessive inheritance of flower color.  The snap dragons have codominant or incomplete dominant where Rr has a pink phenotype.

Answer 2

In pea plants red is dominant over white so genetically:

parents RR (red)  rr(white)

F1 all Rr red

F2 RR Rr rR rr  - first three give red flowers and last 1 white = 25%

Snapdragons red and white are co-dominant, i.e. both colours are expressed. Genetically:

Parents RR (red) WW(white)

F1 all RW pink

F2 RR RW WR WW 1/4 red 1/2 pink 1/4 white