Comparison of LocusLink and Entrez Gene

The Entrez Gene database is a successor to LocusLink. Although LocusLink was discontinued on March 1, 2005, it is possible that you might see or hear that resource name. In case you do, or in case a previous LocusLink user mentions that resource in conversation, it is helpful to be aware of what it covered and how it differs from Entrez Gene. The table below therefore provides a comparison.

	LocusLink	Entrez Gene
Dates Available	April 1999 - March 2005	December 2003 - present
Scope	Included loci from human and approximately 12-15 model or commonly studies organisms such as mouse, rat, zebrafish, etc.	Includes the loci that were present in LocusLink, plus the genes that have been annotated on the complete genomes in Entrez Genomes (i.e., genes annotated on RefSeq NC_* records)
Curation	Records were generally hand-curated by NCBI staff and/or collaborating organism-specific research groups.	Records for human loci and a small number of model or commonly studied organisms continue to be hand-curated, wherever possible, as they were in LocusLink. Records for other organisms, particularly the prokaryotes and lower eukaryotes such as yeast, are automatically generated as described on the preceding slide.
Search Functions	As a research project and prototype system, the search Engine for LocusLink was independent of other NCBI search engines such as Entrez. Search syntaxes and functions were therefore somewhat different than those currently available in Entrez Gene.	The Entrez Gene database provides the same type of interface and search functions available for other Entrez databases. Where necessary and possible, such as on the Limits page and in the list of available search fields, the Entrez interface has been customized for Gene to facilitate data retrieval in ways commonly applied or requested by users. The help documents noted below provide information on general, system-wide Entrez functions and on Gene-specific functions, respectively.
Help Documents	The LocusLink system and help documents are no longer available. They were removed from the NCBI web site when LocusLink was discontinued on March 1, 2005.	The Entrez Help document in the NCBI Help Manual) provides general search tips and techniques that apply across the various Entrez databases. The Entrez Gene Help document (original version; new version in the NCBI Help Manual) and FAQs provide query tips and background information specific to that database. Throughout the help document, you will find "Tips for Previous Users of LocusLink". For example, Table 1 and Table 2 of the original document, and Appendix 1, Appendix 2, Appendix 3 of the new version, provide a comparison of many features found in Entrez Gene and LocusLink.
References	Pruitt KD, Maglott DR. 2001. RefSeq and LocusLink: NCBI gene-centered resources. Nucleic Acids Res. 29(1):137-40 (January 1).   PubMed;  full text Pruitt KD, Katz KS, Sicotte H, Maglott DR. 2000. Introducing RefSeq and LocusLink: curated human genome resources at the NCBI. Trends Genet. 16(1):44-7 (January).   PubMed	Maglott D, Ostell J, Pruitt KD, Tatusova T. 2007. Entrez Gene: gene-centered information at NCBI. Nucleic Acids Res. 35(Database Issue):D26-31 (January 1).   PubMed;  full text Maglott D, Pruitt K, Tatusova T. 2005. Entrez Gene: A Directory of Genes. IN The NCBI handbook [Internet], National Library of Medicine (US), National Center for Biotechnology Information, Bethesda, MD, Chapter 19. Available in the Entrez Books database