Answer: When the protein for a particular gene is formed, the gene is expressed
Gene expression is the process in which the information from a gene is used for the synthesis of protein. The gene code for protein and the protein regulate the function of the cell in the body.
It involves the process of transcription in which a segment of DNA is xeroxed into mRNA by the help of enzyme RNA polymerase. The next step is the translation in which the messenger RNA is decoded in the ribosome to produce a specific amino acid or the polypeptide chain that perform a specific function in the cell.