In molecular biology, a polynucleotide () is a biopolymer composed of nucleotide that are covalently bonded in a chain.
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.
Polynucleotides in organisms
Polynucleotides occur naturally in all living organisms. The
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 polymerase chain reaction (PCR) or
DNA sequencing. Polynucleotides are made artificially from
, smaller nucleotide chains with generally fewer than 30 subunits. A
polymerase 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
abiogenesis. According to the
RNA world hypothesis free-floating
were present in the primitive soup. These were the fundamental molecules that combined in series to form
RNA. Molecules as complex as RNA must have arisen from small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of
purine and
pyrimidine nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian natural selection and
evolution. Nam et al.
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.
Medical use
Fish derived polynucleotide is used in aesthetic medicine as a dermal filler.
[ It has also been found effective in alleviating knee osteoarthritic pain.]
