Doublestranded

Doublestranded, often written as double-stranded, refers to molecules composed of two aligned polymer chains that interact with each other to form a duplex. The most familiar example is double-stranded DNA, which carries genetic information in most organisms. In some contexts, RNA can also be double-stranded when two RNA strands pair with each other or when RNA folds into stable double-stranded regions.

In DNA, the two strands run antiparallel and are held together by complementary base pairing: adenine pairs with thymine and guanine pairs with cytosine. This pairing creates a helical structure, most commonly the B-form in physiological conditions, while double-stranded RNA tends to form an A-form helix. The stability of a double-stranded molecule depends on factors such as length, sequence, and GC content; higher GC content generally increases the melting temperature, making the duplex more resistant to denaturation.

Double-stranded nucleic acids occur in various biological contexts. Most cellular genomes are double-stranded DNA, including chromosomal DNA and circular plasmids. Some viruses deploy double-stranded DNA or double-stranded RNA genomes. In addition, cells frequently form double-stranded regions within single-stranded nucleic acids as they fold or during processes such as replication and transcription.

In laboratory settings, double-stranded nucleic acids are central to many techniques, including polymerase chain reaction, sequencing, cloning, and various forms of hybridization-based assays. Double-stranded DNA is typically required for amplification and analysis, while double-stranded RNA is often used in studies of gene silencing and RNA interference.