The following questions comes from International Biology Olympiad 2014, theoretical part B.
Earlier research suggested that the red flower pigment of plant species was the result of a chemical pathway including multiple steps and that all intermediate pigments were white. Three pure-bred lines with white flowers (White 1, 2 and 3) of this species were crossed with each other and the following ratio of colors were obtained among the progeny:
The question was how many genes control flower color. I completely botched it. Here are my thoughts:
Looking at F2 generation, there are 9 reds + 7 whites = 16 total. (I know it's a ratio.) Generally, having 16 suggests at 2 genes controlling the phenotypes. For example, cross AaBb x AaBb, you'll get 16 phenotypes.
Turns out 2 is incorrect, and I have no clue as to how colors are inherited in this problem. Any suggestions?