A method of altering a eukaryotic cell is provided including transfecting the eukaryotic cell with a nucleic acid en coding RNA complementary to genomic DNA of the eukaryotic cell, transfecting the eukaryotic cell with a nucleic acid encoding an enzyme that interacts with the RNA and cleaves the genomic DNA in a site specific manner, wherein the cell expresses the RNA and the enzyme, the RNA binds to complementary genomic DNA and the enzyme cleaves the genomic DNA in a site specific manner.