The DNA in each chromosome constitutes many genes (as well as vast stretches of noncoding DNA, the function of which is unknown). A gene is any given segment along the DNA that encodes instructions that allow a cell to produce a specific product—typically, a protein such as an enzyme —that initiates one specific action. There are between 50,000 and 100,000 genes in Human cells, and every gene is made up of thousands, even hundreds of thousands, of chemical bases.
