in fission yeast have been sequenced. The lengths of the three centromeres were found to be 34, 65, and 110 kb. This is 300–100 times longer than the centromeres of budding yeast. An extremely high level of conservation (97%) is also seen over 1,780-bp region in the DGS regions of the centromere. This elongation of centromeres and its conservative sequences makes fission yeast a practical model system to use to observe cell division and in humans because of their likeness. PomBase reports over 69% of protein coding genes have human orthologs and over 500 of these are associated with human disease . This makes S. pombe a great system to use to study human genes and disease pathways, especially cell cycle and DNA checkpoint systems. Genetic diversity Biodiversity and evolutionary study of fission yeast was carried out on 161 strains of Schizosaccharomyces pombe collected from 20 countries. Modeling of the evolutionary rate showed that all strains derived from a common ancestor that has lived since ~2,300 years ago. The study also identified a set of 57 strains of fission yeast that each differed by ≥1,900 SNPs;, and all detected 57 strains of fission yeast were prototrophic (able to grow on the same minimal medium as the reference strain). A number of studies on S.pombe genome support the idea that the genetic diversity of fission yeast strains is slightly less than budding yeast. Indeed, only limited variations of S.pombe occur in proliferation in different environments. In addition, the amount of phenotypic variation segregating in fission yeast is less than that seen, in S. cerevisiae. Since most strains of fission yeast were isolated from brewed beverages, there is no ecological or historical context to this dispersal. Cell cycle analysis DNA replication in yeast has been increasingly studied by many researchers. Further understanding of DNA replication, gene expression, and conserved mechanisms in yeast can provide researchers with information on how these systems operate in mammalian cells in general and human cells in particular. Other stages, such as cellular growth and aging, are also observed in yeast in order to understand these mechanisms in more complex systems. S. pombe stationary phase cells undergo chronological aging due to production of reactive oxygen species that cause DNA damages. Most such damages can ordinarily be repaired by DNA base excision repair and nucleotide excision repair. Defects in these repair processes lead to reduced survival. Cytokinesis is one