Deoxyribonucleic acid (DNA) is passed down to you from your parents. It is a long molecule, that is in the shape of a twisted ladder with rungs made of a pair of chemical bases. Chromosomes help package the DNA to fit in the nucleus. There are 6 feet of DNA that is tightly coiled into 23 pairs of chromosomes. The DNA is wrapped around spool-like proteins that run through the centre of each chromosome. The helix is made of two strands of sugar phosphate linked together by pairs of bases. There are four bases and they always make the same pairs; Thymine with Adenine, and Cytosine with Guanine. However, the sequences of bases on the strand are specific to the protein they are going to produce.