A sample containing particles having high-molecular-weight (HMW) DNA is entrapped in a gel matrix, and the gel matrix is exposed to a lysis reagent configured to release the HMW DNA from the particles. The HMW DNA may be purified by subjecting the gel matrix to an electrophoretic field that removes the HMW DNA from the particles, lysis reagents, and/or other sample constituents, from the gel matrix such that the HMW DNA remains. The gel matrix may be subjected with DNA cleavase reagents configured to cleave at specific DNA sequences within the HMW DNA to liberate defined segments of the DNA as fragments of reduced size. The gel matrix may also be subjected to an electrophoretic field, which moves and separates the DNA fragments from uncleaved DNA of the HMW DNA, which remains substantially immobile. The electrophoretically separated DNA fragments may be isolated from the gel matrix.