A. A sample of DNA is added to a gel which binds the molecue together. The DNA fragments of different sizes are spliced together. B. A sample of DNA is added to a gel and exposed to a cureent. The DNA is attracted to the charge and different sized fragments of DNA are sperated. C. The sample of DNA is repeadedly heated and cooled in the presence of DNA polymerase and free nucleotides. Many copies of the fragments of DNA are produced. D. A sample of DNA is added to a gel which holds the fragments in place. In this way, fragment of different length can be distinguished.