This project aims to provide new insights into DNA replication in two phylogenetically related plant species differing in genome size, including the organization of this important process in 3D nuclear space and elucidation of the relationship between transcriptional activity of DNA sequences and their replication. Replication timing of collinear genic regions will be examined in barley, which possesses large genome comprising ~80% of repetitive DNA sequences and in Brachypodium with a small genome, using multidisciplinary approaches including flow cytomwtry, molecular cytogeentics, 3D microscopy, next generation sequencing and bioinformatics.