Answer: Yellow flowers are probably dominant over white flowers.
Explanation: Crossing a purebred individual with another purebred individual means both of them are homozygous for the trait in question. In this case, a homozygous yellow flowers plant is crossed with a homozygous white flowers plant. From this crossing, the offspring is 100% yellow, which means yellow is dominant over white and that the offspring generation is heterozygous for the color trait.
In conclusion, a purebred plant with yellow flowers, whose genotype is WW crossing with a purebred plant with white flowers, whose genotype is ww, produces offspring with genotype Ww, which also have yellow flowers.
