DNA provides the genetic code for all basic body functions from building proteins out of amino acids to regulating the timing and expression of various processes involved with development and growth.
Animals also have structures called mitochondria in their cells.
These cellular organelles are the powerhouses of the cell. In most animals, mtDNA is arranged in a circular fashion. In snails, the mtDNA is between 14,000 and 15,000 base pairs long and encodes 15 genes. In order to figure out the relationships among and within species, we compare the genetic sequence of G, A, T and C's from one animal to the others. Mutations occur in the base pairs, and because of the flexibility and redundancy of the genetic code, these changes can accumulate as populations and species diverge from one another.