The production of multiple copies of DNA can be done by

I. Autoradiography
II. Gel electrophoresis
III. PCR

Autoradiography includes labelling of biomolecules with radioactive material (radioactive thymine for DNA, radioactive uracil for RNA and radioactive S for proteins) followed by localizing these radioactively labelled molecules by applying photosensitive emulsion on the surface of prepared slides. In gel electrophoresis, an electric field is applied to gel that makes the negatively charged DNA fragments to move through a matrix of gel and thereby allows sorting of these fragments according to their size. PCR is a technique amplify the DNA sample in three steps namely denaturation of target DNA (thermal cycle to separate the DNA strands), annealing of primers to the ssDNA and polymerization (extension of primer into complete DNA strand complementary to the template strand).