Genotype refers to the actual genes that an organism has in its DNA. It includes all of the possible traits, or characteristics, that the organism is theoretically capable of having based on its genetic sequences. Phenotype refers to the traits that are actually present in the organism. Things like skin, hair, and eye color are all part of the phenotype. Although phenotypical characteristics are based on underlying genotype, environmental factors can also play a role here. For example, genotype will determine when a tooth might appear, but outside factors will strongly influence how strong the tooth is or how long it might last.