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How are nucleic acids related to proteins?

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Cameron Jacobs eNotes educator | Certified Educator

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You probably know that DNA contains the "instructions for life" and that our genes determine many of our characteristics. You may or may not know that the expression of inherited characteristics is through the action of proteins, large molecules that perform many "jobs" in living organisms. The way DNA controls traits is by providing exact instructions to build proteins. This concept is so fundamental it is called the Central Dogma of biology.

Nucleic acids are DNA and RNA. Both of these are macromolecules, or very large molecules made up of many atoms. They are also both polymers, long chains of smaller, similar subunits or monomers (mono = one; poly = many). The subunits of nucleic acids are called nucleotide bases, or "bases" for short.

Proteins are also macromolecules that have the form of polymers, but they are a different kind of molecule than nucleic acids. The subunits of proteins are called amino acids, and they are joined together in long, unbranched chains as are the bases in nucleic acids. All amino acids have a carboxyl group at one end and an amino group at the other end, but another part of the molecule, called the R group, is different for different amino acids.

Some R groups are bulky and some are not, and some have charge separation while others don't. This causes them to attract or repel when strung together to make a protein, and these effects cause the protein to "fold" or adopt a specific three-dimensional structure. For most proteins, their three-dimensional shape is essential to doing their job, so since the sequence of amino acids determines the shape, the amino acid sequence is essential to protein function. When proteins are made, the correct instructions have to be used to string amino acids together in the right sequence.

This is where the nucleic acids come in. These macromolecules store and transmit information: the instructions for making proteins. Just as computers store information in a sequence of 1s and 0s, DNA and RNA store information as a sequence of bases. Through the process of transcription and translation, sequences of three bases on DNA or RNA specify one amino acid to be added to a protein in the making. There is a sequence that tells the machinery of the cell to start making a protein, and another sequence that tells it to stop.

Thus the information stored in nucleic acids as a sequence of bases is used as instructions to make the correct sequence of amino acids that will become a functional protein. I've attached a picture of a codon chart that shows the translation of nucleotide base sequences to amino acids. The sets of three capital letters represent sequences of three bases, and the sets of three that begin with a capital followed by two lower-case letters are abbreviations for amino acids.

To summarize, the function of nucleic acids is to store and transmit information. The information they store and transmit is the encoded sequence for amino acids that will make functioning proteins. The way genes, or hereditary material, is expressed in the individual is through the function of proteins made according to instructions in the DNA and RNA. This occurs partly because different proteins do many different "jobs," that is, fulfill a wide variety of the functions of life.

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