Anatomy of a Gene
As we have seen previously, most of an animal's genetic material is stored in its chromosomal DNA. This animation shows how that genetic information is packaged in a typical unit of heredity, or gene. With a few exceptions, each gene contains the instructions for the production of an RNA molecule, which in turn serves as the template for producing a string of amino acids called a polypeptide. It is these polypeptides that cause many of the traits we observe.
All of the cells in an animal's various tissues contain virtually identical DNA, no matter how different the cells might appear. Regulatory elements such as promoters help establish this diversity of cell types by determining if, when, and where each gene is expressed. Promoters are generally found at the beginning (or 5' end) of a gene.
In the structural portion of the gene, exons actually code for amino acids, while introns contain regulatory elements along with DNA that has no known function (often called 'junk' DNA). Ultimately, intron sequences are removed from exons in a process called RNA splicing, which is described in the Introns & Exons section of this web site.
Finally, the last part (known as the 3' end) of a gene contains regulatory elements and sequences that help stabilize the RNA product.