Final answer:
The genotype of an individual can be directly known if the phenotype observed is homozygous recessive. In Mendelian genetics, this is evident when recessive traits express themselves in the phenotype, confirming a homozygous recessive genotype. For dominant traits, the genotype may be homozygous dominant or heterozygous and cannot be directly known without further analysis.
Step-by-step explanation:
When considering phenotypes and genotypes, the genotypes of the individuals can be directly known in the case of the homozygous recessive phenotype. For example, using Gregor Mendel's classic pea plant experiments, if the phenotype observed is the recessive green seed color, we can be certain that the genotype is homozygous recessive (yy). However, if the phenotype is the dominant yellow seed, the genotype could be either homozygous dominant (YY) or heterozygous (Yy), meaning it cannot be directly known without further crossing or genetic testing. Phenotypes are the physical expressions or traits of an organism, while genotypes are the specific genetic makeup that codes for these traits. In true-breeding plants with a dominant yellow phenotype (YY) crossed with plants with a recessive green phenotype (yy), all F1 heterozygotes have a yellow phenotype. The use of a Punnett square can help predict the possible genotypes of the F2 generation, as each box in the square represents the diploid genotype of a zygote that could result from the mating.