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Desert Diary


We humans are really good at making up codes. We encode mental concepts so as to share them with others by putting together sounds in specific ways to form words and sentences. Then, in English, we use 26 letters to stand for the sounds that make up the words. Equally impressive, the now outdated Morse code could transmit any message using only two sounds in clusters of one to six.

Yet, as ingenious as we are, codes were "invented" well over 3 billion years before man evolved. All known organisms have their specifications embodied in an identical code. In this, just four chemical compounds in sequences of three form coding units that are strung together to form the blueprints for building and running an organism. This same code, in the form of DNA, works for organisms as diverse as bacteria, cacti, and humans.

As you pass through our desert, you might well keep in mind that you and every living thing around you share this common heritage—tracing back to the first successful organism.
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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.



The DNA codes work by specifying the kinds of amino acids that make up a protein and where they fit in the sequence of amino acids that make up the protein molecule. The vast majority of living organisms use the same three "letters" to stand for the same amino acids. A very few organisms have a code diverted to stand for a different amino acid, while maintaining most of their coding the same as other organisms.



Web Resources

The Genetic Code. A fairly technical discussion, including comments on exceptions to individual codes.