- DNA is made up of subunits which scientists called nucleotides.
- Each nucleotide is made up of a sugar, a phosphate and a base.
- There are 4 different bases in a DNA molecule: adenine (a purine) cytosine (a pyrimidine) guanine (a purine) thymine (a pyrimidine)
- The number of purine bases equals the number of pyrimidine bases
- The number of adenine bases equals the number of thymine bases
- The number of guanine bases equals the number of cytosine bases
- The basic structure of the DNA molecule is helical, with the bases being stacked on top of each other.