Editing Base pair (section)

== Non-canonical base pairing ==
{{Main|Non-canonical base pairing}}
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|caption1=Wobble base pairs
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|image2=Hoogsteen_Watson_Crick_pairing-en.svg
|caption2=Comparison of Hoogsteen to Watson–Crick base pairs.<ref name="Nikolova2">{{cite journal | vauthors = Nikolova EN, Kim E, Wise AA, O'Brien PJ, Andricioaei I, Al-Hashimi HM | title = Transient Hoogsteen base pairs in canonical duplex DNA | journal = Nature | volume = 470 | issue = 7335 | pages = 498–502 | date = February 2011 | pmid = 21270796 | pmc = 3074620 | doi = 10.1038/nature09775 | bibcode = 2011Natur.470..498N }}</ref>
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In addition to the canonical pairing, some conditions can also favour base-pairing with alternative base orientation, and number and geometry of hydrogen bonds. These pairings are accompanied by alterations to the local backbone shape.{{citation needed|date=August 2022}}

The most common of these is the [[wobble base pair]]ing that occurs between [[tRNA]]s and [[mRNA]]s at the third base position of many [[codon]]s during [[Transcription (biology)|transcription]]<ref>{{cite journal | vauthors = Murphy FV, Ramakrishnan V | title = Structure of a purine-purine wobble base pair in the decoding center of the ribosome | journal = Nature Structural & Molecular Biology | volume = 11 | issue = 12 | pages = 1251–1252 | date = December 2004 | pmid = 15558050 | doi = 10.1038/nsmb866 | s2cid = 27022506 }}</ref> and during the charging of tRNAs by some [[Aminoacyl tRNA synthetase|tRNA synthetases]].<ref>{{cite journal | vauthors = Vargas-Rodriguez O, Musier-Forsyth K | title = Structural biology: wobble puts RNA on target | journal = Nature | volume = 510 | issue = 7506 | pages = 480–481 | date = June 2014 | pmid = 24919145 | doi = 10.1038/nature13502 | s2cid = 205239383 }}</ref> They have also been observed in the secondary structures of some RNA sequences.<ref>{{cite journal | vauthors = Garg A, Heinemann U | title = A novel form of RNA double helix based on G·U and C·A<sup>+</sup> wobble base pairing | journal = RNA | volume = 24 | issue = 2 | pages = 209–218 | date = February 2018 | pmid = 29122970 | pmc = 5769748 | doi = 10.1261/rna.064048.117 }}</ref>

Additionally, [[Hoogsteen base pair]]ing (typically written as A•U/T and G•C) can exist in some DNA sequences (e.g. CA and TA dinucleotides) in dynamic equilibrium with standard Watson–Crick pairing.<ref name="Nikolova2" /> They have also been observed in some protein–DNA complexes.<ref name="Aishima">{{cite journal | vauthors = Aishima J, Gitti RK, Noah JE, Gan HH, Schlick T, Wolberger C | title = A Hoogsteen base pair embedded in undistorted B-DNA | journal = Nucleic Acids Research | volume = 30 | issue = 23 | pages = 5244–5252 | date = December 2002 | pmid = 12466549 | pmc = 137974 | doi = 10.1093/nar/gkf661 }}</ref>

In addition to these alternative base pairings, a wide range of base-base hydrogen bonding is observed in RNA secondary and tertiary structure.<ref name=":0">{{cite journal | vauthors = Leontis NB, Westhof E | title = Analysis of RNA motifs | journal = Current Opinion in Structural Biology | volume = 13 | issue = 3 | pages = 300–308 | date = June 2003 | pmid = 12831880 | doi = 10.1016/S0959-440X(03)00076-9 }}</ref> These bonds are often necessary for the precise, complex shape of an RNA, as well as its binding to interaction partners.<ref name=":0" />