D758 Nucleic Acids Research, 2009, Vol. 37, Database issue Figure 1. SNP 129 track details page showing partial information about SNP rs1128456 on chromosome 1. found on the corresponding Genome Browser track details pages. New Gene Sorter columns The Gene Sorter allows users to sort genes using a variety of criteria, including expression pattern or protein homol- ogy, with a large number of user-speciﬁed data ﬁelds dis- played in columns for each gene. The tool provides convenient links back to the Genome Browser or to the gene description on the UCSC Gene details pages, as well as expression proﬁles, protein–protein interaction data and others. Several new columns have been added to the Gene Sorter in the past year for the six model organisms supported by the Gene Sorter: human, mouse, rat, C. elegans, D. melanogaster and yeast. The Intron Size column displays the largest or smallest intron for each gene; the Coding SNPs column gives con- venient access to exon polymorphism information; CDS Score shows a computation of the likelihood that the gene encodes a protein; Gene Category classiﬁes the gene as coding, noncoding, antisense, etc. and Exon Count records the number of exons (Figure 3). NEW DISPLAY FEATURES We have added a number of new display features to the Genome Browser in the past year, many of which are usability improvements based on feedback from the research community. The Base Position track now pro- vides an optional automatic scale bar conﬁgurable through its description page. A Reverse button below the main browser image allows users viewing genes that align on the negative strand to ﬂip the entire display so that the gene of interest appears in the 50-to-30 direction (Figure 2). It is now possible to navigate directly to a single nucleotide by typing the coordinate into the Position box; e.g., chr1:226356466 will locate the SNP rs1128456. (Note that SNPs can still be accessed directly by typing the rs number into the box.) Several enhancements have been added to the track groups below the main browser image. Track groups are now collapsible, allowing the user to hide groups that are not of interest. Tracks can be moved from one group to another, including to the Custom Tracks group at the top, allowing users to collect tracks of interest in one place for a more customized viewing experience. Each of the track group header bars now has a Refresh button that