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Table 1 New symbols and symbol applications in the extended standard human sequence variant nomenclaturea

From: A formalized description of the standard human variant nomenclature in Extended Backus-Naur Form

d Downstream. Position number prefix for coding DNA positions following the end (3') of the transcript. Example: c.*405+d256G>T
n Position number prefix for non-coding DNA positions. Numbering starts at the first nucleotide of the non-coding transcript. Example: n.46G>T
p Suffix to specify protein isoforms in descriptions using LRG sequences (Locus Reference Genomic) [18]. Example: LRG_1p1
t Suffix to specify transcript variants in descriptions using LRG sequences. Example: LRG_1t1
u Upstream. Position number prefix for coding DNA positions upstream (5') of the start of the transcript. Example: c.-110-u256G>T
_i Gene symbol suffix to specify protein isoforms in protein variant descriptions using genomic reference sequences. Example: DMD_i2
_v Gene symbol suffix to specify transcript variants in coding DNA variant descriptions using genomic reference sequences. Example: DMD_v2
^ Exclusive or: to combine DNA descriptions, which are derived from protein level descriptions. Example: backtranslation of p.Ser124Arg, where the Ser-124 codon at c.370_372 is AGC. The variant should be described as c.[370A>C^372C>R] to reflect that arginine can be encoded by six possible codons, AGR (AGC and AGT) and CGN (CGA, CGC, CGG and CGT), respectively.
/ Allele separator in mosaic cases. Used in ISCN [5]. Example: c.[=/85C>T]
// Allele separator in chimaeric cases. Used in ISCN [5]. Example: c.[=//85C>T]
{ } Curly braces enclose "sub-alleles", changes within the range of duplications, inversions, gene conversions and insertions. Example: c.24_65inv{46G>T} (See [4, 5] for details)
; Replaces + in SingleAlleleVarSet, MultiAlleleVars and MultiTranscriptVar
(;) Replaces (+) indicating uncertain phase in UnkAlleleVars. In general, parentheses are used to indicate uncertainty.
  1. a See http://www.hgvs.org/mutnomen for a full list of symbols and their use.