To assess gene distribution across the D-genome chromosomes, we exploit the fact that the Aegilops tauschii genome is completely homologous with the D genome of wheat. Physical maps of each of the seven Ae. tauschii chromosomes will be constructed and a large number of gene loci will be placed on the physical maps. The physical maps will be integrated with the wheat linkage and deletion maps. The distribution of loci integrated into the physical maps will be used to assess the distribution of genes in the D-genome and the distribution and characteristics of gene insulae. The physical maps of the D-genome chromosomes will be compared with the maize phys-ical map and the rice genomic sequence. These comparisons may shed light on the evolution of the global structure of large cereal genomes. The identification and mapping of gene insulae in the wheat D genome will facilitate the discovery and isolation of economically important genes, ultimately allowing the sequencing of the most relevant regions of wheat genomes.