From Encyclopedia Jr, free information reference for Kids
Schematic diagram of a double-stranded nucleic acid. Yellow-green shaded circles represent phosphate; green-hatched circles represent pentose; red-slashed circles represent nitrogenous bases. Solid lines represent covalent bonds; dotted lines represent hydrogen bonds.
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) and locked nucleic acid (LNA), as well as glycol nucleic acid (GNA) and threose nucleic acid (TNA). Each of these is distinguished from naturally occuring DNA or RNA by changes to the backbone of the molecule.
[edit] Chemical structure
The term "nucleic acid", termed because of its prevalence in cellular nuclei, is the generic name of a family of biopolymers. The monomers themselves are called nucleotides. Each monomer 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 specific sugar found in their chain. For example, DNA contains 2-deoxyriboses. Likewise, the nitrogenous bases possible in the two nucleic acids are different: adenine, cytosine, and guanine are possible in both RNA and DNA, while thymine is possible only in DNA and uracil is possible only in RNA. They are really helpful toward carrying our body's code (DNA/RNA) throughout our blood.
Nucleic acids can be either single-stranded or double-stranded. 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. The bases extend from a glycosidic linkage to the 1' carbon of the pentose 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.
