Plants have many advantages for studying eukary­otic DNA replication origins and their relationship to structural and transcriptional domains. Plants like Arabidopsis and rice have small genomes that have been or will be fully se­quenced. Plant tissues at different stages of development and rapidly proliferating, synchroni­zable cultured cells are readily accessible in quantities amenable for bio­chemical analysis. We propose to ex­ploit these properties to con­struct and overlay chromosomal maps of replication origins, matrix attachment regions, modified histones, DNA methylation levels and transcription.