View source for Biology:Polynucleotide

{{short description|Biopolymer molecule composed of nucleotide monomers}}
In [[Biology:Molecular biology|molecular biology]], a '''polynucleotide'''  ({{ety|grc|''πολυς'' (polys)|many}}) is a [[Biology:Biopolymer|biopolymer]] composed of [[Biology:Nucleotide|nucleotide]] [[Chemistry:Monomer|monomer]]s that are covalently bonded in a chain.<ref name=":0">{{MeshName|Polynucleotides}}</ref> [[Biology:DNA|DNA]] (deoxyribonucleic acid) and [[Biology:RNA|RNA]] (ribonucleic acid) are examples of polynucleotides with distinct biological functions. DNA consists of two chains of polynucleotides, with each chain in the form of a [[Helix|helix]] (like a spiral staircase).

==Sequence==
Although DNA and RNA do not generally occur in the same polynucleotide, the four species of nucleotides may occur in any order in the chain. The sequence of DNA or RNA species for a given polynucleotide is the main factor determining its function  in a living organism or a scientific [[Experiment|experiment]].

==Polynucleotides in organisms==
Polynucleotides occur naturally in all living organisms. The [[Biology:Genome|genome]] of an organism consists of complementary pairs of enormously long polynucleotides wound around each other in the form of a double helix. Polynucleotides have a variety of other roles in organisms.

==Polynucleotides in scientific experiments==
Polynucleotides are used in biochemical experiments such as [[Biology:Polymerase chain reaction|polymerase chain reaction]] (PCR)  or DNA sequencing. Polynucleotides are made artificially from [[Chemistry:Oligonucleotide|oligonucleotide]]s, smaller nucleotide chains with generally fewer than 30 subunits. A [[Biology:Polymerase|polymerase]] [[Biology:Enzyme|enzyme]] is used to extend the chain by adding nucleotides according to a pattern specified by the scientist.

==Prebiotic condensation of nucleobases with ribose==

In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible [[Biology:Abiogenesis|prebiotic conditions]].  According to the [[Biology:RNA world|RNA world]] hypothesis free-floating [[Biology:Ribonucleotide|ribonucleotide]]s were present in the primitive soup.  These were the fundamental molecules that combined in series to form [[Biology:RNA|RNA]].  Molecules as complex as RNA must have arisen from small molecules whose reactivity was governed by physico-chemical processes.  RNA is composed of [[Chemistry:Purine|purine]] and [[Chemistry:Pyrimidine|pyrimidine]] nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian natural selection and [[Biology:Evolution|evolution]]. Nam et al.<ref name=":1">Nam I, Nam HG, Zare RN. Abiotic synthesis of purine and pyrimidine ribonucleosides in aqueous microdroplets. Proc Natl Acad Sci U S A. 2018 Jan 2;115(1):36-40. doi: 10.1073/pnas.1718559115. Epub 2017 Dec 18. PMID 29255025; PMCID: PMC5776833</ref> demonstrated the direct condensation of nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Similar results were obtained using wet-dry cycles by Becker et al.<ref>Becker S, Feldmann J, Wiedemann S, Okamura H, Schneider C, Iwan K, Crisp A, Rossa M, Amatov T, Carell T. Unified prebiotically plausible synthesis of pyrimidine and purine RNA ribonucleotides. Science. 2019 Oct 4;366(6461):76-82. doi: 10.1126/science.aax2747. PMID 31604305.</ref>

== Medical Use ==
Fish derived polynucleotide is used in aesthetic medicine as a dermal filler.<ref name=":0">{{MeshName|Polynucleotides}}</ref> It has also been found effective in alleviating knee osteoarthritic pain.<ref name=":1" />{{Failed verification|date=August 2023}}

==References==
{{Reflist}}

{{Nucleobases, nucleosides, and nucleotides}}

[[Category:Organic polymers]]
[[Category:Nucleotides]]

{{Sourceattribution|Polynucleotide}}