Kaplan Nursing Entrance Exam Practice 2026 – Comprehensive Prep

To distinguish between homozygous and heterozygous traits in genetics, particularly for the color of flowers, a test cross is often employed. In this scenario, the goal is to establish the genotype of a red flower, where a homozygous flower would have two identical alleles for red color, while a heterozygous flower would have one red allele and one white allele.

Crossing the red flower with a white plant is particularly effective because if the red flower is heterozygous (having one red allele and one white allele), the offspring will exhibit a mix of phenotypes—some red and some white. In contrast, if the red flower is homozygous (having two red alleles), all offspring will be red. This directly reveals the genotype of the tested red flower.

Similarly, crossing the red flower with another red plant that has a white parent can also yield a mix of offspring if the tested red parent is heterozygous. If it has two homozygous red parents, all offspring would also be red. While this method may confirm red phenotype consistency, it doesn't conclusively distinguish between the homozygous and heterozygous states as effectively as crossing with a white plant does.

Thus, using both