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

A segment of DNA that codes for one protein is referred to as a gene. Genes serve as the basic units of heredity, and they contain the instructions necessary for building the proteins that are essential for the structure and function of living organisms. Each gene carries specific information that dictates the sequence of amino acids in a protein, which ultimately determines the protein's shape and function.

In contrast, chromosomes are structures within cells that are made up of DNA and protein and contain many genes. An allele refers to different versions of a gene that may exist at a specific location on a chromosome, but it does not describe the whole segment coding for a protein. The genome encompasses the complete set of genetic material, including all of the organism's chromosomes and genes, rather than a single segment that codes for one protein. Therefore, identifying a gene as the segment responsible for coding a specific protein provides a clear understanding of genetic function and expression.