Gene expression refers to the process by which information from a gene is used to create a functional product, such as a protein. This process involves two main steps - transcription and translation. During transcription, the DNA sequence of a gene is copied into RNA (ribonucleic acid) molecules. These RNA molecules then serve as templates for the synthesis of proteins during translation, in which amino acids are joined together to form a chain that will fold into its functional three-dimensional shape. Gene expression can be influenced by various factors such as chemical modifications of DNA or histone proteins, epigenetic changes, and environmental conditions.