Disclosed are isolated transposable elements, or isolated DNA sequences which encode a transposase protein or a portion of a transposase protein. The isolated transposable elements or the isolated DNA sequences are members of the mPing/Pong family of transposable elements. The invention also relates to a purified transposase protein, or peptide fragments thereof, encoded by such DNA sequences. Such transposable elements are useful in applications such as the stable introduction of a DNA sequence of interest into a eukaryotic cell. The sequence information disclosed herein is useful in the design of oligonucleotide primers which are useful for the isolation of related members of the mPing/Pong family of transposable elements, or for the detection of transpositions of the transposable elements.