Concept 16.2 Many proteins work together in DNA replication and repair. The specific pairing of nitrogenous bases in DNA was the flash of inspiration that led Watson and Crick to the correct double helix. The possible mechanism for the next step, the accurate replication of DNA, was clear to Watson and Crick from their double helix model. During DNA replication, base pairing enables existing DNA strands to serve as templates for new complementary strands. In a second paper, Watson and Crick published their hypothesis for how DNA replicates. Because each strand is complementary to the other, each can form a template when separated. The order of bases on one strand can be used to add complementary bases and therefore duplicate the pairs of bases exactly. When a cell copies a DNA molecule, each strand serves as a template for ordering nucleotides into a new complementary strand. o One at a time, nucleotides line up along the template strand according to the base-pairing rules. o
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