Polypeptide gene refers to a section of DNA that encodes for a specific polypeptide or peptide chain. In molecular biology, this term is often used interchangeably with protein-coding gene, coding sequence, or open reading frame. Other synonymous terms include ribonucleic acid (RNA) coding sequence, coding exon, and protein-coding region. Furthermore, in genetics, a gene that codes for a protein is also referred to as a gene that is expressed or a gene that is transcribed. These synonyms are frequently used in research and scientific literature to describe the coding region of a gene and the polypeptide or peptide chains that result from its expression.