Yes, RNA is most often single-stranded.
Understanding RNA's Structure
Unlike DNA, which typically exists as a double helix, RNA molecules are usually single-stranded. This means they consist of a single chain of nucleotides, rather than two complementary strands bound together. Each nucleotide in the RNA chain is composed of a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), uracil (U), cytosine (C), or guanine (G). The single-stranded nature of RNA allows it to fold into a variety of complex three-dimensional structures, crucial for its diverse functions within the cell.
Several sources confirm this:
- Genome.gov: Explicitly states that "Unlike DNA, however, RNA is most often single-stranded." https://www.genome.gov/genetics-glossary/Ribonucleic-Acid-RNA
- ACS Publications: Discusses the sequence-dependent conformations of single-stranded RNA. https://pubs.acs.org/doi/full/10.1021/jacs.9b04461
- Science Magazine: Describes the design and synthesis of single-stranded RNA for origami structures. https://www.science.org/doi/10.1126/science.aao2648
- Nature: Mentions that Toll-like receptor 8 recognizes single-stranded RNA (ssRNA). https://www.nature.com/articles/nsmb.2943
- Wikipedia: Reinforces that RNA is "usually a single-stranded molecule (ssRNA)." https://en.wikipedia.org/wiki/RNA
While RNA is predominantly single-stranded, it's important to note that some RNA molecules can form double-stranded regions through intramolecular base pairing. These secondary structures are essential for RNA function.
Examples of Single-Stranded RNA's Roles:
- mRNA (messenger RNA): Carries genetic information from DNA to ribosomes for protein synthesis.
- tRNA (transfer RNA): Carries amino acids to ribosomes during translation.
- rRNA (ribosomal RNA): A structural component of ribosomes.
- Viral RNA: The genetic material of many viruses.
