What term refers to a sequence of DNA that codes for a protein and determines a trait?

The term that refers to a sequence of DNA that codes for a protein and determines a trait is "gene." Genes serve as the fundamental units of heredity in all living organisms. Each gene contains the information necessary to produce specific proteins, which play crucial roles in the function and structure of cells. These proteins ultimately influence the traits observed in an organism, such as eye color or height.

In contrast, a chromosome is a long strand of DNA that contains many genes and is located within the nucleus of a cell. An allele is a specific version of a gene that may vary between individuals, contributing to the diversity of traits. Phenotype refers to the observable characteristics or traits of an organism, which are shaped by the underlying genotype (the genetic makeup, including both alleles). Therefore, the clear connection between genes and traits solidifies why "gene" is the appropriate choice for this question.