What is a segment of DNA that codes for a trait or protein called?

A segment of DNA that codes for a specific trait or protein is referred to as a gene. Genes are the fundamental units of heredity and play a crucial role in determining the characteristics of an organism. They consist of sequences of nucleotides that provide the instructions for making proteins, which perform a wide variety of functions in the body.

While chromosomes are structures that carry genes and are made up of DNA, they represent a higher level of organization. Alleles are different forms of a gene that can exist at a specific locus on a chromosome, influencing variations in traits. The genotype refers to the genetic makeup of an organism, specifically the combination of alleles present, but it does not describe the specific segment that codes directly for traits or proteins. Thus, identifying a gene as the segment of DNA that directly encodes these traits is essential for understanding the mechanisms of heredity and the expression of genetic characteristics.