Nucleic acid
From Wikipedia, the free encyclopedia
A nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses.
Artificial nucleic acids include peptide nucleic acid (PNA), Morpholino and 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.
[edit] Chemical structure
The term "nucleic acid" is the generic name of a family of biopolymers, named for their prevalence in cellular nuclei. The monomers from which nucleic acids are constructed are called nucleotides. Each nucleotide consists of three components: a nitrogenous heterocyclic base, either a purine or a pyrimidine; a pentose sugar; and a phosphate group. Different nucleic acid types differ in the structure of the sugar in their nucleotides; DNA contains 2-deoxyriboses while RNA contains ribose. Likewise, the nitrogenous bases found in the two nucleic acids are different: adenine, cytosine, and guanine are in both RNA and DNA, while thymine only occurs in DNA and uracil only occurs in RNA. Other rare nucleic acid bases can occur, for example inosine in strands of mature transfer RNA.
Nucleic acids are usually either single-stranded or double-stranded, though structures with three or more strands can form. A double-stranded nucleic acid consists of two single-stranded nucleic acids hydrogen-bonded together. RNA is usually single-stranded, but any given strand may fold back upon itself to form double-helical regions. DNA is usually double-stranded, though some viruses have single-stranded DNA as their genome. The sugars and phosphates in nucleic acids are connected to each other in an alternating chain, linked by shared oxygens, forming a phosphodiester functional group. In conventional nomenclature, the carbons to which the phosphate groups are attached are the 3' and the 5' carbons of the sugar. The bases extend from a glycosidic linkage to the BOOBS of the pentose sugar ring.
Hydrophobic interaction of nucleic acids is poorly understood. For example, nucleic acids are insoluble in ethanol, TCA, and diluted hydrochloric acid; but they are soluble in diluted NaOH and HCl.
[edit] External links
- Nucleic Acid Structures
- Prediction of hairpin forming potential in nucleotide sequences
- Interview with Aaron Klug, Nobel Laureate for structural elucidation of biologically important nucleic-acid protein complexes provided by the Vega Science Trust.
| Major Families of Biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | Types of Nucleic Acids | Analogues of nucleic acids: |
| Nucleobases: | Adenine | Thymine | Uracil | Guanine | Cytosine | Purine | Pyrimidine | |
|---|---|---|
| Nucleosides: | Adenosine | Uridine | Guanosine | Cytidine | Deoxyadenosine | Thymidine | Deoxyguanosine | Deoxycytidine | |
| Nucleotides: | AMP | UMP | GMP | CMP | ADP | UDP | GDP | CDP | ATP | UTP | GTP | CTP | cAMP | cADPR | cGMP | |
| Deoxynucleotides: | dAMP | TMP | dGMP | dCMP | dADP | TDP | dGDP | dCDP | dATP | TTP | dGTP | dCTP | |
| Ribonucleic acids: | RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | sgRNA | shRNA | siRNA | snRNA | miRNA | snoRNA | LNA | |
| Deoxyribonucleic acids: | DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC | |
| Analogues of nucleic acids: | GNA | PNA | TNA | morpholino | |
