Why is DNA relevant to amino acids ?
DNA is a sequence of nucleotides. There are four nucleotides: adenine, thymine, cytosine, guanine. The exact sequence of these determines the code of each gene. When DNA is transcribed (the first step in expression of the gene), RNA is synthesized using this code. The RNA is a complementary copy of one strand of the DNA. The RNA leaves the nucleus and in the cytoplasm it is translated into a protein. Each set of three contiguous RNA nucleotides codes for a single amino acid, and the protein is made of a chain of amino acids hooked to one another. So each set of three nucleotides in the DNA eventually codes for one amino acid in the final protein that is made from a given gene. The nucleotides and amino acids are not similar chemically, and it is the protein synthesis machinery of the cell that is needed to translate one code into the other. A good description of this can be found in Biology, by Neil Campbell, published by Benjamin Cummings.
