Testcross.

An organism exhibiting a dominant trait (purple flowers). can be either homozygous dominant or heterozygous.

To determine its genotype, the individual with the dominant phenotype is crossed with a recessive phenotype (white flowers), since the latter's genotype has to be homozygous recessive.





By observing the phenotypes of the offspring, we can deduce the genotype of the purple-flowered parent.