Polynukleotidets

Polynukleotidets, often referred to in English as polynucleotides, are polymers composed of nucleotides linked by phosphodiester bonds. They form the chemical basis of genetic material in living organisms. Each nucleotide consists of a sugar molecule (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base (adenine, cytosine, guanine, and thymine in DNA; adenine, cytosine, guanine, and uracil in RNA). The phosphate–sugar backbone gives polynucleotides a negatively charged, hydrophilic exterior, while the base sequence encodes information.

Polynucleotides can exist as double-stranded molecules (DNA) or single-stranded molecules (RNA). DNA typically forms two antiparallel strands in a right-handed double helix, with base pairing between A and T and between G and C. RNA is generally single-stranded and can fold into diverse structures that enable catalytic activity or interactions with other molecules.

Biological roles include storing and transmitting genetic information (DNA) and converting that information into functional products (RNA). Messenger RNA carries information for protein synthesis, while transfer RNA and ribosomal RNA participate in translation. Numerous regulatory RNAs influence gene expression, and some RNA molecules act as catalysts (ribozymes).

Synthesis of polynucleotides occurs by condensation reactions catalyzed by polymerases, forming phosphodiester linkages in the 5' to 3' direction. In cells, replication and transcription generate and copy polynucleotides, which vary in length from a few dozen to millions of nucleotides. The term encompasses natural DNA and RNA as well as synthetic or modified polymers used in research and medicine.