Genomes, genes and junk: the large-scale organization of plant chromosomes

Plants from wide taxonomic groupings have similar genes and ordering of genes along the chromosomes. However, the repetitive DNA, much of no known function and often constituting the majority of the genome, varies extensively from species to species in absolute amount, sequence and dispersion pattern. Despite this, it is known that families of repeated DNA motifs each have a characteristic genomic location within a genus, and that there are different constraints on the evolution of repetitive DNA and genes, There are now enough data about different types of repetitive DNA - from sequencing, Southern analysis and in situ hybridization - to build a model of the organization of a typical plant genome, and apply it to gene cloning, evolutionary studies and gene transfer.