Purines, Pyrimidines, and Nucleotides
Purines, pyrimidines, and nucleotides are ubiquitous molecules found throughout a mammalian as well as a human body. In one form or another, these molecules serve a variety of roles. Nucleotides are molecular building blocks or subunits of nucleic acids such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). These subunits are also called monomers. The synthesis of purines, pyrimidines, and nucleotides is an important part of mammalian metabolism. Errors in purine and pyrimidine synthesis and metabolism, inborn or acquired, often are the cause of disease or ultimately lead to disease.
Nucleotides and their structure
A nucleotide is made up of three units:
- A nitrogen-containing base,
- A five-carbon sugar,
- One two three phosphate groups.
There are five common 
IUPAC nucleotide codes with ambiguity
Symbol | Meaning | Origin of designation | Fw |
G | G | Guanine | 151.12 |
A | A | Adenine | 135.12 |
T | T | Thymine | 126.11 |
C | C | Cytosine | 111.1 |
U | U | Uracil | 112.08 |
M | A or C | aMino |
|
R | G or A | puRine |
|
W | A or T | Weak interactions |
|
S | C or G | Strong interaction |
|
Y | T or C | pYrimidine |
|
K | G or T | Keto |
|
V | G or C or A | not- T (not-U), V follows U |
|
H | A or C or T | not-G, H follows G in the alphabet |
|
D | A or G or T | not-C, D follows C |
|
B | C or G or T | not-A, B follows A |
|
X | G or A or T or C |
|
|
N | G or A or T or C | aNy |
|
Reference:
Cornish-Bowden A. Nomenclature for incompletely specified bases in nucleic acid sequences: recommendations 1984. Nucleic Acids Research. 1985;13(9):3021-3030.
INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY AND INTERNATIONAL UNION OF BIOCHEMISTRY ABBREVIATIONS AND SYMBOLS FOR NUCLEIC ACIDS, POLYNUCLEOTIDES AND THEIR CONSTITUENTS RULES APPROVED 1974 Issued by the JUPAC—IUB Commission on Biochemical Nomenclature