What does DNA do?

Table of the nucleic acid template patterns for the formation of amino acids in protein sequences (from wikipedia). These triplet patterns are formed from the four bases U (uracil in RNAs), T (thymine in DNA), C (cytosine), A (adenine), and G (guanine), and are often described as the genetic ‘code’, but it is important to understand that this usage of the word ‘code’ is metaphorical and can be confusing. A real code is an intentional encryption used by humans to communicate. The genetic ‘code’ is not intentional in that sense. The more neutral word ‘template’ is better. It also expresses the fact that templates are used only when required (activated), they are not themselves active causes.

DNA sequences are templates for the formation of RNAs, some of which are in turn used as templates for the formation of proteins. Only RNAs and proteins are specified by the DNA sequences. RNAs and proteins then cooperate with many metabolites and other components of the organism to generate the numerous interlocking biochemical pathways. These pathways in turn work within the three dimensional structure of the cells, tissues and organs of the body. But this three-dimensional structure is not to be found in the one-dimensional DNA sequences. How then do cells know how to form such an intricate biological mechanism of precise functionality? The answer is self-templating. The three-dimensional structures copy themselves, first by growing in size and then, when the cell becomes large enough to divide, the structures are divided between the two cells. Each daughter cell therefore inherits its complete complement of structure as well as inheriting the genome.

For further aspects of the answer to this question see  Immortal genes?