RNA is typically single-stranded but can fold back on itself through complementary base pairing (including a stable G-U wobble pair unique to RNA) to form secondary structures. The simplest of these is the stem-loop (hairpin), which arises from an inverted repeat within the sequence, producing a paired stem and an unpaired loop; larger RNAs (ribozymes, ribosomal RNA, transfer RNA) display extensive secondary structure including mismatches, unpaired regions, and bulges. This self-pairing occurs in the A-form helical geometry, the same conformation adopted by RNA-RNA and RNA-DNA duplexes, distinguishing it from the B-form typical of double-stranded DNA.
RNA is typically single-stranded but can fold back on itself through complementary base pairing (including a stable G-U wobble pair unique to RNA) to form secondary structures. The simplest of these …