Final answer:
A gene is a segment of DNA that carries the code for making a specific polypeptide chain. Genes are responsible for the production of proteins, and each protein is made up of one or more polypeptide chains.
Step-by-step explanation:
A gene is a segment of DNA that carries the code for making a specific polypeptide chain. This means that the statement 'A gene is a DNA segment that is used to make a polypeptide only' is true. Genes are responsible for the production of proteins, and each protein is made up of one or more polypeptide chains. The DNA sequence in a gene determines the sequence of amino acids in a polypeptide, which ultimately determines the structure and function of the protein.