Scientists use a variety of tools to analyze DNA. As this animation produced by WGBH and Digizyme, Inc. shows, gel electrophoresis enables them to determine the size of DNA molecules. Using this technique, together with other tools such as PCR reactions and restriction digestion, scientists can compare the molecular variations of two or more samples to determine such things as the identity of the DNA's source or the presence or absence of a particular gene or DNA fragment.
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