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Chapter 7 : DNA Replication
DNA replication is a topic usually presented in 9th-grade biology. The essential fact of DNA replication is that the base-pairing rules make it very easy to generate two identical new helices from one helix. The first part is appropriate for young students; more advanced students will perform both parts of the lesson. The first activity described in this chapter is a simple (and necessarily inaccurate) paper simulation of DNA replication. The second activity is a student reading about DNA polymerase, the central DNA replication enzyme. The background information in the introduction that follows contains far more detail about DNA replication. The two aspects of DNA synthesis that your advanced students need to know are that synthesis is unidirectional and that it absolutely requires a primer. Not surprisingly, the characteristics of DNA polymerase determine the overall features of DNA replication inside the cell and in the test tube. The feature of DNA replication means that DNA synthesis is unidirectional, from 5' to 3'. Uni-directionality presents a problem for chromosome replication that is discussed in this chapter. Chromosomal DNA replication is usually initiated at specific sites along the DNA called replication origins. Instead, several different strategies circumvent the problem created by the specificity of DNA replication enzymes.