Theoretical part of this diploma thesis gives a brief characteristic of human mobile elements (transposons), which represents nearly 50% of human genome. It provides basic transposon clasification and describes types of transposons present in hunam genome, as well as mobilization, activation and regulation mechanisms. The work also deals with the domestication of transposons, describes the ways in which TE contribute to DNA damage and summarizes the diseases caused by mutagenic activity of transposons in the human genome. Conclusion of theoretical part describes next-generation sequencing technologies (NGS). As practical part, data from RNA-seq experimet were analyzed in order to compare differen transposon activity in normal and cancer cells from prostate and colorectal tissues. As like as publicly available sophisticated tools (TopHat), new scripts were created to analyze these data. The results show that cancer cells exhibit overexpression of transposons. This corresponds with the published results and suggests a connection of transposon activation with cancer development.