doublestrand

Doublestrand, often written as double-stranded, refers to nucleic acids in which two polymer chains form a duplex. The term is commonly applied to double-stranded DNA, the primary genetic material in most organisms, and to double-stranded RNA, which occurs in some viruses and cellular processes.

In canonical double-stranded nucleic acids, the two strands run antiparallel and are linked by hydrogen bonds between complementary bases. DNA strands use A with T and G with C; RNA pairs A with U in structures like dsRNA. The sugar-phosphate backbones are on the exterior, with bases stacked inside to form a double helix; in DNA, the common form is B-DNA, while dsRNA often adopts an A-form helix.

dsDNA is typically more chemically stable than ssDNA and provides a durable genetic repository. Its double-stranded nature requires replication by separation of the strands and synthesis of complementary strands, generally in a semi-conservative manner. dsRNA plays roles in gene regulation and defense, including RNA interference, and is found in certain viruses as their genomes.

Physical properties include melting temperature, which increases with GC content due to three hydrogen bonds per G-C pair. Denaturation separates strands for techniques like PCR, sequencing, and hybridization assays. The stability and structure of double-strands influence replication fidelity, repair, and transcription.

In biology and medicine, double-stranded nucleic acids are central to genetics, virology, and molecular biology research. Examples include dsDNA in human chromosomes and many viruses; dsRNA is characteristic of others. Analysis and manipulation rely on understanding base pairing, strand orientation, and duplex stability.