The term "silent gene" refers to a genetic sequence that does not result in the production of a functional protein. Synonyms for this term include "non-coding gene," "non-expressed gene," and "silent mutation." Non-coding genes are sequences of DNA that do not code for a protein, but may have other important roles in gene regulation and functioning. Non-expressed genes are those that are present in an organism's DNA but are not active in producing a protein. Silent mutations are changes in a gene sequence that do not result in a different amino acid being produced in the resulting protein, and therefore do not alter the protein's function. These terms are important in understanding the complexity of the genetic code and its role in organism biology and evolution.