polynukleotid

Polynucleotide is a polymer composed of many nucleotides linked by phosphodiester bonds. Each nucleotide contains a sugar molecule (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, and guanine in DNA; adenine, uracil, cytosine, and guanine in RNA). The sequence of bases encodes genetic information or carries structural or catalytic roles in RNA.

Polynucleotides form the primary molecules of genetic material in most organisms. DNA is the main polynucleotide in cells and typically exists as a double-stranded, antiparallel helix with base pairing between adenine and thymine and between guanine and cytosine. RNA is usually single-stranded but can fold into complex structures through intramolecular base pairing; thymine is replaced by uracil in RNA.

Structure and orientation: The sugar-phosphate backbone runs in the 5' to 3' direction, giving polynucleotides polarity. The two strands of DNA are complementary and run in opposite directions, enabling replication and transcription. RNA can form diverse secondary structures that support its functional roles.

Synthesis and function: Polynucleotides are synthesized by polymerases using nucleoside triphosphates. DNA replication copies the genome, while transcription produces RNA from a DNA template. RNA molecules participate in translation, catalysis (ribozymes), regulation, and other cellular processes. Polynucleotides can also be chemically synthesized for research and therapeutic applications, such as oligonucleotides and antisense technologies. Polynucleotides can be linear or, in some genomes, circular.