- DNA stands for  desoxyribose nucleic acid

- DNA  is a very large molecule made up of a long chain of sub-units

- The sub-units are called nucleotides

- Each nucleotide is made up of sugar called desoxyribose, phosphate group -PO4 and an organic base

- The most common organic bases are: Adenine. Thymine, Guanine and Cytosine

- A molecule of DNA is formed by millions of nucleotides joined together in a long chain