Welcome to the UCSC Genome Browser website. This site contains the reference sequence and working draft assemblies for a large collection of genomes. It also provides portals to the ENCODE and Neandertal projects.

WARNING: This is a test site. Data and tools here are under construction, have not been quality reviewed, and are subject to change at any time. For high-quality reviewed annotations on our production server, visit http://genome.ucsc.edu.

We encourage you to explore these sequences with our tools. The Genome Browser zooms and scrolls over chromosomes, showing the work of annotators worldwide. The Gene Sorter shows expression, homology and other information on groups of genes that can be related in many ways. Blat quickly maps your sequence to the genome. The Table Browser provides convenient access to the underlying database. VisiGene lets you browse through a large collection of in situ mouse and frog images to examine expression patterns. Genome Graphs allows you to upload and display genome-wide data sets.

The UCSC Genome Browser is developed and maintained by the Genome Bioinformatics Group, a cross-departmental team within the Center for Biomolecular Science and Engineering (CBSE) at the University of California Santa Cruz (UCSC). If you have feedback or questions concerning the tools or data on this website, feel free to contact us on our public mailing list.

To receive announcements of new genome assembly releases, new software features, updates and training seminars by email, subscribe to the genome-announce mailing list.

06 March 2014 - The new GRCh38 Human Genome Browser is here!

In the final days of 2013, the Genome Reference Consortium (GRC) released the eagerly awaited GRCh38 human genome assembly, the first major revision of the human genome in more than four years. During the past two months, the UCSC team has been hard at work building a browser that will let our users explore the new assembly using their favorite Genome Browser features and tools. Today we're announcing the release of a preliminary browser on the GRCh38 assembly. Although we still have plenty of work ahead of us in constructing the rich feature set that our users have come to expect, this early release will allow you to take a peek at what's new.

Starting with this release, the UCSC Genome Browser version numbers for human assemblies will match those of the GRC to minimize version confusion. Hence, the GRCh38 assembly is referred to as hg38 in Genome Browser datasets and documentation. We've also made some slight changes to our chromosome naming scheme that affect primarily the names of haplotype chromosomes, unplaced contigs and unlocalized contigs. For more details about this, see the hg38 gateway page.

What's new in GRCh38?

• Alternate sequences - Several human chromosomal regions exhibit sufficient variability to prevent adequate representation by a single sequence. To address this, the GRCh38 assembly provides alternate sequence for selected variant regions through the inclusion of alternate loci scaffolds (or alt loci). Alt loci are separate accessioned sequences that are aligned to reference chromosomes. This assembly contains 261 alt loci, many of which are associated with the LRC/KIR area of chr19 and the MHC region on chr6. (See the sequences page for a complete list of the reference chromosomes and alternate sequences in GRCh38.)
• Centromere representation - Debuting in this release, the large megabase-sized gaps that were previously used to represent centromeric regions in human assemblies have been replaced by sequences from centromere models created by Karen Miga et al., using centromere databases developed during her work in the Willard lab at Duke University and analysis software developed while working in the Kent lab at UCSC. The models, which provide the approximate repeat number and order for each centromere, will be useful for read mapping and variation studies.
• Mitochondrial genome - The mitochondrial reference sequence included in the GRCh38 assembly and hg38 Genome Browser (termed "chrM" in the browser) is the Revised Cambridge Reference Sequence (rCRS) from MITOMAP with GenBank accession number J01415.2 and RefSeq accession number NC_012920.1. This differs from the chrM sequence (RefSeq accession number NC_001907) used by the previous hg19 Genome Browser, which was not updated when the GRCh37 assembly later transitioned to the new version.
• Sequence updates - Several erroneous bases and misassembled regions in GRCh37 have been corrected in the GRCh38 assembly, and more than 100 gaps have been filled or reduced. Much of the data used to improve the reference sequence was obtained from other genome sequencing and analysis projects, such as the 1000 Genomes Project.
• Analysis set - The GRCh38 assembly offers an "analysis set" that was created to accommodate next generation sequencing read alignment pipelines. Several GRCh38 regions have been eliminated from this set to improve read mapping. The analysis set may be downloaded from the Genome Browser downloads page.

For more information about the files included in the GRCh38 GenBank submission, see the GRCh38 README. The GRCh38 GenBank record provides a detailed array of statistics about this assembly. Bulk downloads of the sequence and annotation data may be obtained from the Genome Browser FTP server or the Downloads page. The annotation tracks for this browser were generated by UCSC and collaborators worldwide.

Much more to come! This initial release of the hg38 Genome Browser provides a rudimentary set of annotations. Many of our annotations rely on data sets from external contributors (such as our popular SNPs tracks) or require massive computational effort (our comparative genomics tracks). In the upcoming months/years, we will release many more annotation tracks as they become available. To stay abreast of new datasets, join our genome-announce mailing list or follow us on twitter.

To highlight a region: Click and hold the mouse button on one edge of the desired area to be highlighted in the Base Position track, drag the mouse right or left to highlight the selection area, then release the mouse button. Click the "Highlight" button on the "drag-and-select" popup. More details about this new feature can be found on our help page.

Credit goes to Tim Dreszer, Larry Meyer, Robert Kuhn and Luvina Guruvadoo for the design, development and testing of this feature. Additional testing was also provided by several members of the QA team.

The Genome Browser software, sequence and annotation data are freely available for use with these conditions. A license is required for commercial use of the software. For assistance with questions or problems regarding the UCSC Genome Browser software, database, genome assemblies, or release cycles, click here.

Program-driven use of this software is limited to a maximum of one hit every 15 seconds and no more than 5,000 hits per day.

The UCSC Genome Browser was created by the Genome Bioinformatics Group of UC Santa Cruz. Software Copyright (c) The Regents of the University of California. All rights reserved.