Question

If the flower of a plant can be either white or pink, the gene that determines flower color has how many alleles?
A.1
B.2
C.3
D.4

Answer 1

There is not enough info to definitely answer this question.

In the first place, flower color can depend entirely on environmental factors. When I was an undergrad in genetics class, I took some pure breeding white snap dragons and watered them with diluted red food coloring to prove a point. Guess what color they turned. My lab instructor was not impressed. In that case there was only one allele for flower pigmentation but I was able to grow pinkish flowers from them anyway.

In the second place, epistatic effects do not preclude the possibility that three or more alleles (of different genes) affect pigment producing pathways in the flower petals.

All that said, the answer is probably two.