| http://digfir-published.macmillanusa.com/lodish_animation/a0401_transcription_mech.html | Chapter 4. Basic Transcriptional Mechanisms
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| http://digfir-published.macmillanusa.com/lodish_animation/a0401_transcription_mech_dlap.xml | DLAP questions | 519bca41b11c0f1368000050 |