Question

Snapdragons produce red, white, or pink flowers in an incomplete dominance inheritance pattern in which pink is the blended phenotype. Can a cross of any two non-red snapdragons produce red snapdragons? Use a Punnett square to support your answer.

Answer 1

No — only some non-red crosses can produce red. With incomplete dominance (R = red, W = white), the genotypes are:
- RR = red
- RW = pink (blended)
- WW = white

Consider the three possible crosses of two non-red parents (pink = RW or white = WW):

1) RW × RW (pink × pink)
Gametes: R, W × R, W

| | R | W |
|---|---|---|
| R | RR| RW|
| W | RW| WW|

Offspring: 1/4 RR (red), 1/2 RW (pink), 1/4 WW (white). => Red can appear (25%).

2) RW × WW (pink × white)
Gametes: R, W × W, W

| | W | W |
|---|---|---|
| R | RW| RW|
| W | WW| WW|

Offspring: 1/2 RW (pink), 1/2 WW (white). => No red.

3) WW × WW (white × white)
All gametes W:

All offspring WW (white). => No red.

Conclusion: Two non-red snapdragons will produce red offspring only if both parents are pink (RW × RW).