This composite track contains information about single nucleotide polymorphisms (SNPs) and small insertions and deletions (indels) — collectively Simple Nucleotide Polymorphisms — from dbSNP, available from ftp.ncbi.nih.gov/snp. You can click into each track for a version/subset-specific description.

This collection includes numbered versions of the entire dbSNP datasets (All SNP) as well as three tracks with subsets of the items in that version. Here is information on each of the subsets:

• dbSNP 153: The dbSNP build 153 is composed of 5 subtracks. Click the track for a description of the subtracks.
• Common SNPs: SNPs that have a minor allele frequency of at least 1% and are mapped to a single location in the reference genome assembly. Frequency data are not available for all SNPs, so this subset is incomplete.
• Flagged SNPs: SNPs flagged as clinically associated by dbSNP, mapped to a single location in the reference genome assembly, and not known to have a minor allele frequency of at least 1%. Frequency data are not available for all SNPs, so this subset may include some SNPs whose true minor allele frequency is 1% or greater.
• Mult. SNPs: SNPs that have been mapped to multiple locations in the reference genome assembly.

The default maximum weight for this track is 1, so unless the setting is changed in the track controls, SNPs that map to multiple genomic locations will be omitted from display. When a SNP's flanking sequences map to multiple locations in the reference genome, it calls into question whether there is true variation at those sites, or whether the sequences at those sites are merely highly similar but not identical.

To view the full description, click here.