[Table, Table 3. Allele definitions define the class of the variation in dbSNP.] - The NCBI Handbook

dbSNP variation class^{a, b}	Rules for assigning allele classes	Sample allele definition	Class code in Sybase, ASN.1, and XML^c
Single Nucleotide Variations (SNVs)^a	Strictly defined as single base substitutions involving A, T, C, or G. Formerly called “SNP”. Name changed to “SNV” to emphasize that the dbSNP database contains both rare and polymorphic variants.	A/T	1
Deletion/Insertion Variations (DIVs)^a	Designated using the full sequence of the insertion as one allele, and either a fully defined string for the variant allele or a “-” character to specify the deleted allele. This class will be assigned to a variation if the variation alleles are of different lengths or if one of the alleles is deleted (“-”). Formerly called “DIP”. Name changed to “DIV” to emphasize that the dbSNP database contains both rare and polymorphic variants.	T/-/CCTA/G	2
Heterozygous sequence^a	The term heterozygous is used to specify a region detected by certain methods that do not resolve the polymorphism into a specific sequence motif. In these cases, a unique flanking sequence must be provided to define a sequence context for the variation.	(heterozygous)	3
Microsatellite or short tandem repeat (STR)^a	Alleles are designated by providing the repeat motif and the copy number for each allele. Expansion of the allele repeat motif designated in dbSNP into full-length sequence will be only an approximation of the true genomic sequence because many microsatellite markers are not fully sequenced and are resolved as size variants only.	(CAC)8/9/10/11	4
Named variant^a	Applies to insertion/deletion polymorphisms of longer sequence features, such as retroposon dimorphism for Alu or line elements. These variations frequently include a deletion “-” indicator for the absent allele.	(alu) / -	5
No-variation^a	Reports may be submitted for segments of sequence that are assayed and determined to be invariant in the sample.	(NoVariation)	6
Mixed^b		Mix of other classes	7
Multi-Nucleotide Variation (MNV)^a	Assigned to variations that are multi-base variations of a single, common length. Formerly called “MNP”. Name changed to “MNV” to emphasize that the dbSNP database contains both rare and polymorphic variants.	GGA/AGT	8

dbSNP variation class^{a, b}

Rules for assigning allele classes

Sample allele definition

Class code in Sybase, ASN.1, and XML^c

Single Nucleotide Variations (SNVs)^a

Strictly defined as single base substitutions involving A, T, C, or G.

Formerly called “SNP”. Name changed to “SNV” to emphasize that the dbSNP database contains both rare and polymorphic variants.

A/T

Deletion/Insertion Variations (DIVs)^a

Designated using the full sequence of the insertion as one allele, and either a fully defined string for the variant allele or a “-” character to specify the deleted allele. This class will be assigned to a variation if the variation alleles are of different lengths or if one of the alleles is deleted (“-”).

Formerly called “DIP”. Name changed to “DIV” to emphasize that the dbSNP database contains both rare and polymorphic variants.

T/-/CCTA/G

Heterozygous sequence^a

The term heterozygous is used to specify a region detected by certain methods that do not resolve the polymorphism into a specific sequence motif. In these cases, a unique flanking sequence must be provided to define a sequence context for the variation.

(heterozygous)

Microsatellite or short tandem repeat (STR)^a

Alleles are designated by providing the repeat motif and the copy number for each allele. Expansion of the allele repeat motif designated in dbSNP into full-length sequence will be only an approximation of the true genomic sequence because many microsatellite markers are not fully sequenced and are resolved as size variants only.

(CAC)8/9/10/11

Named variant^a

Applies to insertion/deletion polymorphisms of longer sequence features, such as retroposon dimorphism for Alu or line elements. These variations frequently include a deletion “-” indicator for the absent allele.

(alu) / -

No-variation^a

Reports may be submitted for segments of sequence that are assayed and determined to be invariant in the sample.

(NoVariation)

Mixed^b

Mix of other classes

Multi-Nucleotide Variation (MNV)^a

Assigned to variations that are multi-base variations of a single, common length.

Formerly called “MNP”. Name changed to “MNV” to emphasize that the dbSNP database contains both rare and polymorphic variants.

GGA/AGT

From: Chapter 5, The Single Nucleotide Polymorphism Database (dbSNP) of Nucleotide Sequence Variation

The NCBI Handbook [Internet].

McEntyre J, Ostell J, editors.

Bethesda (MD): National Center for Biotechnology Information (US); 2002-.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.