Nucleic+Acids

Nucleic acids are biological molecules essential for life, and include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information.

Nucleic acids were discovered by Friedrich Miescher in 1869. Experimental __studies__ of nucleic acids constitute a major part of modern biological and medical research, and form a foundation for genome and forensic science, as well as the biotechnology and pharmaceutical industries.



DNA-Deoxyribonucleic acid
A nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms is deoxyribonucleic acid. DNA molecules is the long-term storage of information and DNA is often compared to a set of blueprints is the main role since it contains the instructions needed to construct other components of cells. This is broken down into four separate forms as follow: adenine, thymine, uracil (RNA form of thymine), and guanine. These four basic building blocks make up the coding for specific proteins. All life on earth contains a similar amount of DNA, and the same base pairs. The differences in complexity we see between say a person and a frog are contributed not to more, less or different DNA, but to slight differences in the sequencing of those base pairs.

Ribonucleic acid- RNA
Ribonucleic acid (RNA) functions in converting genetic information from genes into the amino acid sequences of proteins. The three universal types of RNA include transfer RNA (tRNA), messenger RNA (mRNA), and ribosomal RNA (rRNA). The messenger RNA carries a sort of photocopy of a DNA sequence to a ribosome, where transfer RNA collects nucleic acids and carries them to the ribosome for protein synthesis.

Occurrence and nomenclature
The term //nucleic acid// is the overall name for DNA and RNA, members of a family of [|biopolymers], [|[6]] and is synonymous with [|//polynucleotide//]. Nucleic acids were named for their initial discovery within the [|nucleus], and for the presence of phosphate groups (related to phosphoric acid). Although first discovered within the [|nucleus] of [|eukaryotic] cells, nucleic acids are now known to be found in all life forms, including within [|bacteria], [|archaea] , [|mitochondria] , [|chloroplasts] , [|viruses] and [|viroids]. All living cells and organelles contain both DNA and RNA, while viruses contain either DNA or RNA, but usually not both. [|[7]] The basic component of biological nucleic acids is the [|nucleotide], each of which contains a pentose sugar ( [|ribose] or [|deoxyribose] ), a [|phosphate] group, and a [|nucleobase]. Nucleic acids are also generated within the laboratory, through the use of enzymes [|[8]] (DNA and RNA polymerases) and by [|solid-phase chemical synthesis]. The chemical methods also enable the generation of altered nucleic acids that are not found in nature, [|[9]] for example [|peptide nucleic acids].

Molecular composition and size
Nucleic acids can vary in size, but are generally very large molecules. Indeed, DNA molecules are probably the largest individual molecules known. Well-studied biological nucleic acid molecules range in size from 21 nucleotides ( [|small interfering RNA] ) to large chromosomes ( [|human chromosome 1] is a single molecule that contains 247 million base pairs [|[11]] ).

In most cases, naturally occurring DNA molecules are double-stranded and RNA molecules are single-stranded. There are numerous exceptions, however—some viruses have genomes made of [|double-stranded RNA] and other viruses have [|single-stranded DNA] genomes, and, in some circumstances, nucleic acid structures with [|three] or [|four] strands can form.

Nucleic acids are linear [|polymers] (chains) of nucleotides. Each nucleotide consists of three components: a [|purine] or [|pyrimidine] [|nucleobase] (sometimes termed //nitrogenous base// or simply //base//), a [|pentose] [|sugar], and a [|phosphate] group. The substructure consisting of a nucleobase plus sugar is termed a [|nucleoside]. Nucleic acid types differ in the structure of the sugar in their nucleotides - DNA contains 2'- [|deoxyribose] while RNA contains [|ribose] (where the only difference is the presence of a [|hydroxyl group] ). Also, the nucleobases found in the two nucleic acid types are different: [|adenine], [|cytosine] , and [|guanine] are found in both RNA and DNA, while [|thymine] occurs in DNA and [|uracil] occurs in RNA.

The sugars and phosphates in nucleic acids are connected to each other in an alternating chain (sugar-phosphate backbone) through [|phosphodiester] linkages. [|[10]] In [|conventional nomenclature], the carbons to which the phosphate groups attach are the 3'-end and the 5'-end carbons of the sugar. This gives nucleic acids [|directionality], and the ends of nucleic acid molecules are referred to as 5'-end and 3'-end. The nucleobases are joined to the sugars via an N-glycosidic linkage involving a nucleobase ring nitrogen (N-1 for pyrimidines and N-9 for purines) and the 1' carbon of the pentose sugar ring.

Non-standard nucleosides are also found in both RNA and DNA and usually arise from modification of the standard nucleosides within the DNA molecule or the primary (initial) RNA transcript. [|Transfer RNA] (tRNA) molecules contain a particularly large number of modified nucleosides. [|[12]]