sentences:  In fission yeast such as "S. pombe", the formation and maintenance of the heterochromatin organization is regulated by RNA-induced transcriptional silencing, a form of RNA interference responsible for genomic maintenance in many organisms.Mating type regions have also been well studied in budding yeast "S. cerevisiae" and in the fungus "Neurospora crassa".In the budding yeast "Saccharomyces cerevisiae", mating-type is determined by two non-homologous alleles at the mating-type locus.