The term Oxford Grid was first used by V.A. McKusick in the 8th edition of Mendelian Inheritance in Man (MIM; 1988; p. cxvi) to describe a diagram summarising loci orthologous in mouse and human. This diagram had first appeared in the second of a series of four papers on mouse-human homologies (Buckle et al. 1984) from the Genetics Laboratory in Oxford and the nearby MRC unit at Harwell. The original concept was devised by Professor J. (John) H. Edwards in the early 1980s. He extended the basic concept in collaboration with Jo Dicks to include pairwise chromosome grids (an expanded single rectangle of the grid), one-to-many grids (one chromosome of one species versus all relevant chromosomes of the other species), and multi-species grids (one chromosome of one species versus all other species). For a description of these extensions, click here. Loci were mapped only to whole chromosomes in the early grids: each locus was indicated by a point arbitrarily, or randomly, placed within the relevant rectangle to display the general pattern of homology. As soon as substantial positional data were available, it was possible to indicate location within each of the two chromosomes with their short arms uppermost or to the left, with any defined measure of position on each chromosome. In position-based grids, short 'kinks' are suggestive of an erroneous inferred order in one species. Lone loci in any rectangle, 'orphans', require careful checking as they are likely to be due to mapping errors in the data, since short insertions are very rare. Grids can also be used within species to compare paternal and maternal gametes, physical and genetic maps (with their identical order and variable inter-locus distances), and to display discrepancies in maps from different sources. The term 'Oxford Grid is frequently used to denote a grid consisting entirely of squares, devoid of points conveying position or locus density or emphasizing 'orphans', thereby omitting its main feature. Later John Edwards in Oxford, Jo Dicks (Oxford, and later Norwich) and Jean Thierry-Mieg (Montpelier, later Bethesda), developed software for drawing grids in ACeDB. Ian Leonard (Oxford) subsequently developed this software to use the resources of recent browsers, with advanced internet access through HTML files. While ACeDB is ideal for this purpose, its limited application to mammals in other centres and the demands of advanced interactive graphics made it ill-suited for Internet usage. With the explosion of comparative-mapping information, and with the vast resources of the web now so readily accessible, the Australian National Genomic Information Service (ANGIS) is hosting the Oxford Grid Project, which commenced in June 2003. This web site reflects the combined contributions of John Edwards (Oxford), Frank Nicholas (University of Sydney), Stefan Gregory (ANGIS), Matthew Hobbs (CRC for Innovative Dairy Products) and Jonathan Usmar (SheepGenomics), and the many colleagues who have generated public-domain data. The Oxford Grid Project is still very much a work in progress. In particular, its facilities are far from being as automated as John Edwards envisioned, and links have still to be created directly to the locus/trait databases such as OMIM and OMIA. But it does present grids for each of a range of mammals against other mammals, with each grid being zoomable to either a particular rectangle (from which each orthologue is hyperlinked to relevant locus and mapping databases at NCBI and Ensembl and elsewhere) or to an entire row, representing the entire orthologous information available for a particular chromosome in the reference species. There is also a tool for generating a “grid of grids” a set of zoomable Oxford grids for each pair-wise combination of the ever-increasing number of sequenced annotated species, based on lists of orthologues obtainable automatically from Ensembl. The grid of grids (which currently involves 34 species) is automatically updated with each new release of the Ensembl orthologue database. Adaptation of Oxford grids Oxford grids have been adapted for use in a variety of comparative mapping circumstances, including agricultural crops (Odland et al. 2006; Yang and Gingle, 2005; ftp://cggc.agtec.uga.edu/OxfordGrid/). They have also been used as the basis for the development of mathematical measures of the extent of conservation of synteny between pairs of species (e.g. Housworth and Postlethwait, 2002). A very useful modified form of Oxford grid has been developed by The Jackson Laboratory, in which each rectangle contains the number of orthologues in that particular pair of chromosomes. Clicking on the number retrieves details of all those orthologues. The Oxford Grid Project is still in its infancy, with much work still in progress. References Buckle, V.J., Edwards, J.H., Evans, E.P., Jonasson, J.A., Lyon, M.F., Peters, J., Searle, A.G. and Wedd, N.S. (1984) Chromosome maps of man and mouse II. Clinical Genetics 26: 1-11 Edwards, J.H. (1991) The Oxford grid. Annals of Human Genetics 55: 17-31 Housworth, E.A. and Postlethwait, J. (2002) Measures of synteny conservation between species pairs. Genetics 162, 441-8 McKusick, V.A.(1988) Mendelian Inheritance in Man. Catalogs of Human Genes and Genetic Disorders. (8th edition) Baltimore: Johns Hopkins University Press Odland, W., Baumgarten, A. & Phillips, R. (2006) Ancestral rice blocks define multiple related regions in the maize genome. Crop Sci. 46, 41-48 Yang, H. & Gingle, A.R. (2005) OxfordGrid: a web interface for pairwise comparative map views. Bioinformatics 21, 4307-4308