Tuesday 16 September 2003
Definition: A nucleic acid is a macromolecule composed of chains of monomeric nucleotides.
Monomeric nucleotides have three major parts:
a five-carbon sugar,
a phosphate group,
a nitrogen-containing base.
The sugar is either a ribose, forming RNA or a deoxyribose making DNA.
The nitrogen containing base can be in the form a single or double carbon ring structure.
- The single carbon ring structures, known as the pyrimidines, have three forms: cytosine and thymine, which are found in DNA, and uracil which is found only in RNA.
- The double carbon ring structures, known as the purines, have two forms: guanine, and adenine.
The four different types of DNA nucleotides are then linked together, forming a large double-stranded molecule (deoxyribonucleic acid, DNA).
Each strand’s backbone consists of joined sugars and phospate groups of the adjacent nucleotides. The nucleotides are then connected to form a double-stranded molecule that twists helically, like a spiral staircase.
The DNA molecule is the carrier of all genetic material within the cell. It has a very basic structure in which large amounts of information can be stored by a simple arrangement of nucleotides.
Artificial nucleic acids
Artificial nucleic acids include:
peptide nucleic acid (PNA),
locked nucleic acid (LNA), as well as glycol nucleic acid (GNA) and threose nucleic acid (TNA).
Each of these is distinguished from naturally-occurring DNA or RNA by changes to the backbone of the molecule.