Editing Nucleotide (section)

== Abbreviation codes for degenerate bases ==
{{main|Nucleic acid notation}}
The [[IUPAC]] has designated the symbols for nucleotides.<ref name="iupac">{{cite web |url=http://www.chem.qmul.ac.uk/iubmb/misc/naseq.html |author=Nomenclature Committee of the International Union of Biochemistry (NC-IUB) |title=Nomenclature for Incompletely Specified Bases in Nucleic Acid Sequences |date=1984 |access-date=2008-02-04}}</ref> Apart from the five (A, G, C, T/U) bases, often degenerate bases are used especially for designing [[Primer (molecular biology)|PCR primers]]. These nucleotide codes are listed here.  Some primer sequences may also include the character "I", which codes for the non-standard nucleotide [[inosine]].  Inosine occurs in [[tRNAs]] and will pair with adenine, cytosine, or thymine.  This character does not appear in the following table, however, because it does not represent a degeneracy.  While inosine can serve a similar function as the degeneracy "H", it is an actual nucleotide, rather than a representation of a mix of nucleotides that covers each possible pairing needed.

{| class="wikitable" style="vertical-align:top; margin-left:25px; margin-top:10px; margin-right:25px; margin-bottom:25px; text-align:center;"
|-
! Symbol<ref name="iupac"/> !! Description !!colspan=5| Bases represented
|-
| '''A''' || align="left" | '''a'''denine || A || || || ||rowspan=5| 1
|-
| '''C''' || align="left" | '''c'''ytosine || || C || ||
|-
| '''G''' || align="left" | '''g'''uanine || || || G ||
|-
| '''T''' || align="left" | '''t'''hymine || || || || T
|-
| '''U''' || align="left" | '''u'''racil || || || || U
|- bgcolor=#e8e8e8
| '''W''' ||align=left| '''w'''eak || A || || || T ||rowspan=6| 2
|- bgcolor=#e8e8e8
| '''S''' ||align=left| '''s'''trong || || C || G ||
|- bgcolor=#e8e8e8
| '''M''' ||align=left| [[Amine|a'''m'''ino]] || A || C || ||
|- bgcolor=#e8e8e8
| '''K''' ||align=left| [[Ketone|'''k'''eto]] || || || G || T
|- bgcolor=#e8e8e8
| '''R''' ||align=left| [[Purine|pu'''r'''ine]] || A || || G ||
|- bgcolor=#e8e8e8
| '''Y''' ||align=left| [[Pyrimidine|p'''y'''rimidine]] || || C || || T
|-
| '''B''' ||align=left|  not A ('''B''' comes after A) || || C || G || T  ||rowspan=4| 3
|-
| '''D''' ||align=left|  not C ('''D''' comes after C) || A || || G || T
|-
| '''H''' ||align=left| not G ('''H''' comes after G)|| A || C || || T
|-
| '''V''' ||align=left| not T ('''V''' comes after T and U) || A || C || G ||
|- bgcolor=#e8e8e8
| '''N''' ||align=left|  a'''n'''y base (not a gap) || A || C || G || T || 4
|}