When a cell makes a protein…the gene is active or being expressed.
One gene can make more than one kind of protein when Exons (see DNA Transcription) splice together in different combinations. This is why there are many more proteins than genes.
As of now we know there to be 30,000-40,000 human genes, but more than 120,000 possible proteins in humans. The shape and folding pattern of each protein is also thought to give the protein its function.
Collaborative consultation on website genetics and genomics from Dr. Stephen M. Carleton, Assistant Professor, Department of Anatomy and Cell Biology, SUNY Health Science Center at Brooklyn.