The main topic that I am discussing in my thesis is about methods for detecting changes in DNA caused by CRISPR/Cas9. In the introductory part of the paper I describe the development of the natural CRISPR/Cas9 system through history. The following is a description of the structure of the CRISPR locus and the structural organization and architecture of the SpCas9 domain, where I focused on describing the key components for the operation of the CRISPR/Cas9 system. Then I introduced how the engineered CRISPR/Cas9 from SpCas9 works and its use as a molecular tool, with an emphasis on possible changes in DNA and possible applications. In the second part of the diploma thesis I described various methods for detecting changes in DNA caused by CRISPR/Cas9, the possibilities of their use, and the advantages and disadvantages of individual methods.