Internal-loops (also termed interior loops) in

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

are found where the double stranded RNA separates due to no

Watson-Crick-Franklin base pairing A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DN ...

between the

nucleotides Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules wi ...

. Internal-loops differ from

Stem-loop Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence wh ...

s as they occur in middle of a stretch of double stranded RNA. The non-canonicoal residues result in the double helix becoming distorted due to unwinding, unstacking and kinking. Internal-loops can be classified as either symmetrical or asymmetrical, with some asymmetrical internal-loops, also known as bulges. Many important structural motifs are composed of internal loops such as the C-loop, the docking-elbow, kink-turns (k-turn), the right-angle, the sarcin/ricin loops (also called bulged-G motifs), the twist-up motif and the UAA/GAN internal loop motif.

References

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See also