A trait, as related to genetics, is a specific characteristic of an individual. Traits can be determined by genes, environmental factors or by a combination of both. Traits can be qualitative (such as eye color) or quantitative (such as height or blood pressure). A given trait is part of an individual’s overall phenotype.
Trait. When you think of the word traits, you might think of personality traits like compassionate or a good sense of humor. In genetics, traits are characteristics about humans and other living organisms that can be described or measured. Traits can be physical or behavioral. Researchers and clinicians are interested in what causes people to have certain traits and not others, especially when those traits give us clues about causes and treatments of illness. When someone has a combination of a few particular traits, that might give us clues about how to diagnose a medical condition. And we can compare those traits to similar combinations of traits in other people to study how different diseases might be related to each other.
NHGRI Bioethics Core