| http://digfir-published.macmillanusa.com/lodish_animation/a0406_bidirectional_repl.html | Chapter 4. Bidirectional Replication of DNA
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| http://digfir-published.macmillanusa.com/lodish_animation/a0406_bidirectional_repl_dlap.xml | DLAP questions | 519bca41b11c0f136800005a |