Composition of DNA
DNA is shaped as a double helix. Which is a twisted ladder shape. DNA is a nucleic acid which is made up of nucleotides. A nucleotide is made up of a nitrogen base, sugar and phosphate. The four nitrogen bases are adenine, guanine, cytosine, thymine. The variety of nitrogen bases cause the genetic diversity. There are rules to pairing. Adenine can only pair with thymine and guanine can only pair with cytosine.