A gene is a working subunit of a DNA molecule.
A gene is any given segment along the DNA carrying a particular set of instructions that allows a cell to produce a specific product--typically, a protein such as an enzyme. There are about 25,000 genes, and every gene is made up of thousands, even hundreds of thousands, of chemical bases.
![Gene Subunits](https://webarchive.library.unt.edu/eot2008/20090509123954im_/http://www.cancer.gov/images/Documents/2bb8687b-eb2b-4e62-ba30-a0572dee414e/cancer6.jpg)
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