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Molecular Genetics

This review discusses the molecular processes of transcription and translation in the lac operon. It explains how the lac operon functions in the absence and presence of lactose, and how regulatory genes and repressor proteins play a role in gene expression. Includes helpful animations.

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Molecular Genetics

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Presentation Transcript

  1. Molecular Genetics

  2. Transcription (Review)

  3. Translation (Review)

  4. The lac Operon Function • DNA (lacZ, lacY, lacA)  mRNA  protein (lactose digest enzymes)

  5. Environment: lactose absent • Regulatory gene synthesizes protein (lac repressor) • Lac repressor binds to the operator • RNA polymerase cannot bind to the promoter • Lactose digesting enzymes are not synthesized

  6. Environment: lactose present • Regulatory gene synthesizes protein (lac repressor) • Lactose binds to the lac repressor • Repressor changes shape and is unable to bind to promoter • RNA polymerase transcribes mRNA & translates protein

  7. Lac Operon Animation • http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation27.html

  8. Environment: low levels of trp • Regulatory gene synthesizes protein (trp repressor) • Trp repressor is initially an inactive repressor protein • RNA polymerase transcribes 5 operon genes into mRNA • mRNA is translated into protein (enzymes that synthesize typ)

  9. Environment: high levels of trp • Regulatory gene synthesizes protein (trp repressor) • Trp present in cell binds to & activates the repressor • Repressor binds to the operator • RNA polymerase cannot bind to the promoter • Trp synthesizing enzymes are not produced

  10. Operon animation • http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120080/bio26.swf::The%20Tryptophan%20Repressor

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