DNA stands for deoxyribonucleic acid which tells you that DNA contains deoxyribose (a 5-carbon sugar) and nucleic acid (molecule made up of nucleotides)
Nucleotides consists of a sugar molecule attached to a nitrogen base and a phosphate group. nucleotides have 3 parts sugar, nitrogen base and phosphate DNA is in the shape of a double helix and was discovered by Watson and Crick
Base pair rules
DNA is a double stranded molecule - the tow strands are connected by the nitrogen bases. Adenine can only pair with thymine ( and vice versa) Guanine can only par with cytosine ( and vice versa)
The molecular structure of the 4 bases fall under two categories: Purines- double ring structures- adenine and guanine are purines Pyrimidines- single ring structures- thymine and cytosine are pyrimidines Purines always bond with pyrimidines (as per the base pairing rules).