Gene duplication and the structure of eukaryotic genomes

A simple method for understanding how gene duplication has contributed to g enomic structure was applied to the complete genomes of Caenorhabditis eleg ans, Drosophila melanogaster, and yeast Saccharomyces cerevisiae. By this m ethod, the genes belonging to gene families (the paranome) were identified, and the extent of sharing of two or more families between genomic windows was compared with that expected under a null model. The results showed sign ificant evidence of duplication of genomic blocks in both C. elegans and ye ast. In C. elegans, the five block duplications identified all occurred int ra-chromosomally, and all but one occurred quite recently. In yeast, by con trast, 39 duplicated blocks were identified, and all but one of these was i nter-chromosomal. Of these 39 blocks, 28 showed evidence of ancient duplica tion, possibly as a result of an ancient polyploidization event. By contras t, three blocks showed evidence of very recent duplication, while seven oth ers showed a mixture of ancient and recent duplication events. Thus, duplic ation of genomic blocks has been an ongoing feature of yeast evolution over the past 200-300 million years.