Final answer:
The genotype of a specific trait can be identified using a test cross, which crosses a dominant phenotype with an unknown genotype with a homozygous recessive individual to observe the offspring's phenotypes.
Step-by-step explanation:
An easy way to identify the genotype of a specific trait is by performing a test cross. This involves crossing an individual expressing the dominant phenotype with an unknown genotype with a homozygous recessive individual. If all offspring show the dominant trait, the unknown parent is homozygous dominant. If there's a 1:1 ratio of dominant to recessive phenotypes, the unknown parent is heterozygous.
To use concrete examples, a pea plant with violet flowers has a dominant trait, abbreviated as V. If it's crossed with a plant with known white flowers (recessive, hence genotype vv), the resulting offspring can help reveal the violet-flowered plant's genotype (either VV or Vv). The appearance of any white-flowered plant among the offspring indicates that the violet plant is heterozygous (Vv).