Answer to Question #84686 in Molecular Biology for anu
Contamination is presence of foreign material in a sample. It could occur, when samples are occasionally mixed, studied cultures are not pure, investigator's DNA appears in samples, or some DNA present in the surrounding enters the samples. It is possible that foreign DNA appears in samples, because aseptic and sterile precautions are not followed, for example, samples are touched by fingers, tips are not changed after each sample, investigator does not wear gloves. Being attentive and following of rules while working with samples can help prevent contamination.