Maize exhibits levels of structural variation (SV) of non-repeat sequences that are unprecedented among higher eukaryotes. This SV includes hundreds of copy number variants (CNVs) and thousands of presence/absence variants (PAVs). Many of the PAVs contain intact, expressed, single-copy genes that are present in one haplotype but absent from another. The goal of this project is to test the hypothesis that differences in gene copy number (both gains and losses) contribute to the extraordinary phenotypic diversity and plasticity of maize. Maize is a good model for these studies because it exhibits a rapid decay of linkage disequilibrium (LD) and because a draft genome sequence of the B73 inbred and mapping populations are available. As a first step, the "Zeanome", a near-complete set of genes present in B73, other maize lines and the wild ancestor of maize (teosinte), is being defined using transcriptomic data.