DNA is located mainly in the nucleus, but can also be found in other cell structures called mitochondria. Since the nucleus is so small, the DNA needs to be tightly packaged into bundles known as chromosomes.
The DNA that is found in the cell structures, known as mitochondria, is responsible for providing the energy that the cell needs to function. Many organisms also have sets of DNA that are responsible for aiding in reproduction. These are known as sex cells and help create a new organism. In humans and many other animals, the sex cells combine to form two separate sets of DNA that will make up the cells of the new organism. Some organisms only take DNA from the mother cells.
DNA is made up of parts called nucleotides. These parts are responsible for building the rest of the cell structures that are present in organisms. Nucleotides are made up of phosphate groups, sugar groups and a nitrogen base. A strand of DNA is formed when these nucleotides link together. The sugar groups and the phosphate groups alternate throughout the entire strand of DNA. The nitrogen base is the base of the DNA strand and remains constant throughout the entire strand.