Nucleotides are the subunits of DNA. The four nucleotides are adenine, cytosine, guanine and thymine. Each of the four bases has three components, a phosphate group, a deoxyribose sugar and a nitrogen-containing base.
*Remember*
C and G will always pair together (Cytosine and Guanine)
A and T will always pair together (Adenine and Thymine)
