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In Chapter 33, we learned that DNA is the archival form of genetic information. An archive is a historical record or document, which makes referring to DNA as an archive or archival information particularly appropriate; DNA contains the information to generate a new individual organism—be it a bacterium, a ficus, or a human being, depending on its source. In other words, DNA contains the blueprint for the development of the organism as well as the evolutionary history of an organism.

If DNA is the archival information, who are the archivists of the cell? Such vital information must be handled carefully. Just as the monk depicted in the illustration above carefully copied manuscripts for preservation, molecular equivalents copy and preserve DNA. The molecular equivalents of these archivists are enzymes called DNA polymerases. As discussed in Chapter 33, the DNA double helix is a stable structure, as should be the case for archival information. Because of this stability, the rate of spontaneous strand separation is negligible. However, strand separation is necessary to synthesize copies of genetic information for the next cell generation. Thus, energy is required for this process, and other molecules are required to assist the DNA polymerases to gain access to the sequence information. Other enzymes and proteins separate the strands and prepare the DNA for copying by the master archivists, the DNA polymerases.

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We begin this chapter with an examination of the enzymes taking part in DNA replication. We then see how these enzymes are coordinated to complete the complex process of DNA replication. Finally, we examine some of the special difficulties in eukaryotic replication.