Previous work has shown that, in the large genomes of three Gramineae [rice, maize, and barley: 415, 2,500, and 5,300 megabases (Mb), respectively] most genes are clustered in long DNA segments (collectively called the "gene space") that represent a small fraction (12-24%) of nuclear DNA, cover a very narrow (0.8-1.6%) GC range, and are separated by vast expanses of gene-empty sequences. In the...
