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== Variant of base pairing ==
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[[File:Hoogsteen_Watson_Crick_pairing-en.svg|thumb|251x251px|Chemical structures for Watson-Crick and Hoogsteen A•T and G•C+ base pairs.<ref name="Nikolova">{{cite journal|author1=Evgenia N. Nikolova|author2=Eunae Kim|author3=Abigail A. Wise|author4=Patrick J. O'Brien|author5=Ioan Andricioaei|author6=Hashim M. Al-Hashimi|year=2011|title=Transient Hoogsteen base pairs in canonical duplex DNA|journal=Nature|volume=470|issue=7335|pages=498–502|bibcode=2011Natur.470..498N|doi=10.1038/nature09775|pmc=3074620|pmid=21270796}}</ref>]]▼
|image1=Wobble.svg
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. The most common of these is [[Hoogsteen base pairing]] (typically written as A•U/T and G•C). Hoogsteen base pairs can exist in some DNA sequences (e.g. CA and TA dinucleotides) in dynamic equilibrium with standard Watson–Crick pairing.<ref name="Nikolova2">{{cite journal|author1=Evgenia N. Nikolova|author2=Eunae Kim|author3=Abigail A. Wise|author4=Patrick J. O'Brien|author5=Ioan Andricioaei|author6=Hashim M. Al-Hashimi|year=2011|title=Transient Hoogsteen base pairs in canonical duplex DNA|journal=Nature|volume=470|issue=7335|pages=498–502|bibcode=2011Natur.470..498N|doi=10.1038/nature09775|pmc=3074620|pmid=21270796}}</ref> They have also been observed in some protein–DNA complexes.<ref name="Aishima">{{cite journal|author=Jun Aishima, Rossitza K. Gitti, Joyce E. Noah, Hin Hark Gan, [[Tamar Schlick]], Cynthia Wolberger|year=2002|title=A Hoogsteen base pair embedded in undistorted B‐DNA|journal=Nucleic Acids Res|volume=30|issue=23|pages=5244–5252|doi=10.1093/nar/gkf661|pmc=137974|pmid=12466549}}</ref>▼
|caption1=Wobble base pairs
|width1=75
|image2=Hoogsteen_Watson_Crick_pairing-en.svg
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|width2=285
}}
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.
The most common of these is the Wobble base pairing.
Additionally, [[Hoogsteen base pairing]] (typically written as A•U/T and G•C) can exist
[[File:Wobble.svg|right|thumb|480x480px|Wobble base pairs for [[inosine]] and [[guanine]]]]
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==Length measurements==<!-- This section is linked from [[KB]] -->
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