Genome comparisons highlight similarity and diversity within the eukaryotic kingdoms

In 2000, the number of completely sequenced eukaryotic genomes increased to four. The addition of Drosophila and Arabidopsis into this cohort permits additional insights into the processes thai have shaped evolution. Analysis and comparisons of both completed genomes and partially sequenced genomes have already shed light on mechanisms such as gene duplication and gene los s that have long been hypothesized to be major forces in speciation. Indeed , duplicate gene pairs in Saccharomyces, Arabidopsis, Caenorhabditis and Dr osophila are high: 30%, 60%, 48% and 40%, respectively. Evidence of horizon tal gene-transfer, thought to be a major evolutionary force in bacteria, ha s been found in Arabidopsis. The release of the 'first draft' of the human genome sequence in 2000 heralds a new stage of biological study. Understand ing the as-yet-unannotated human genome will be largely based on conclusion s, techniques and tools developed during the analysis and comparison of the genome of these four model organisms.