Over time, genomes acquire changes by genetic mutation. The resulting variety of DNA changes are known as genetic variation. These changes come in a variety that make up two general categories: single base pair changes (single nucleotide polymorphisms or SNPs) or structural variation (like chromosomal rearrangements, large deletions or insertions).
These variations can result in changes in phenotypes, including causing diseases known as genetic disorders. A vast amount of data is being generated to probe relationships between genetic variation and phenotypes. The NCBI collects and presents some of this data in the Variation databases.
The NCBI Variation databases can be divided into two categories:
The Archival Databases (dbSNP and dbVar) contain records of variation submitted by investigators all over the world and how common they are in specific populations. They do not directly contain information about the consequences of these variations but they link to medical genetic databases that do.
The Medical Genetics Databases (dbGaP, ClinVar, GTR, MedGen and OMIM) contain clinical information about the results of these variants.
See the figure below for a diagram of the databases and how they relate to biological concepts.
The NCBI also provides a suite of tools to search and visualize the variation data. Here are a few:
See the following diagram for how these tools relate to the variation databases.