What is a nucleotide?

A nucleotide is the basic unit that makes up DNA. A singular nucleotide is made up of x3 components:

1. A base (A, T, C or G)
2. 5 Carbon sugar (deoxyribose = DNA or ribose = RNA)
3. Phosphate group (forms a bond between the sugar molecules in a DNA chain = phosphodiester bond) Bases There are x4 different nitrogenous bases that comprise DNA.
4. Adenosine
5. Cytosine
6. Thymine
7. Guanine

There are two groups of nucleotides pyrimidines and purines

Pyrimidines Thymine and Cytosine are the smallest of the 4 bases. With only 1 ring in their structure. In RNA, Thymine is replaced by Uracil all other bases are the same

Purines Adenosine and Guanine are purines. Their structure contains a pyrimidine ring + a smaller 5 sided ring. Therefore making a 2 ringed structure.