Transposons have coexisted with eukaryotes for thousands of years and through their coexistence have become integrated in many organisms genomes. Colloquially known as jumping genes', transposons can move within and between genomes allowing for this integration.
While there are many positive effects of transposons in their host eukaryotic genomes, there are some instances of mutagenic effects that TEs have on genomes leading to disease and malignant genetic alterations.