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Molecular Genetics

Molecular Genetics. Gene Regulation. Gene Regulation. At any given moment, a cell is only transcribing some of the genes contained in its DNA Cells can selectively control which genes are being transcribed

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Molecular Genetics

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  1. Molecular Genetics Gene Regulation

  2. Gene Regulation • At any given moment, a cell is only transcribing some of the genes contained in its DNA • Cells can selectively control which genes are being transcribed • All the cells in your body have the same DNA, but cells differentiate when they selectively transcribe different genes

  3. Prokaryotic Gene Regulation • Operons = segments of DNA that control transcription of a gene • Promoter = where RNA poly binds to begin transcription • Operator = where a repressor protein can bind to block RNA poly • Structural genes = code for related enzymes that lead to a particular end product • Regulatory gene = produces repressor proteins (bind to operator to block RNA poly) or activator proteins (assist RNA poly in attaching to promoter)

  4. Operon

  5. lacOperon Found in E. coli Controls breakdown of lactose Structural genes code for enzymes that control uptake and breakdown of lactose (only needed when lactose is present) Inducible (normal off, repressor bound) Lactose binds to repressor to allow RNA poly to transcribe structural genes

  6. lacOperon

  7. lacOperon http://www.youtube.com/watch?v=oBwtxdI1zvk (3:25) http://www.youtube.com/watch?v=Sie1HAMPlV8 (3:57) *must watch!

  8. trpOperon Also found in E. coli Controls synthesis of the amino acid tryptophan Regulatory gene produces inactive repressor (doesn’t bind to operator), so tryptophan is normally produced Repressible (normally on, repressor not bound) If tryptophan is available in the environment, the bacteria doesn’t need to make it Tryptophan binds to repressor to activate it (binds to operator to block RNA poly)

  9. trpOperon

  10. trpOperon https://www.youtube.com/watch?v=1arC3WkQNVQ (1:07)

  11. Eukaryotic Gene Regulation Regulatory proteins (activators and repressors) affect RNA poly binding to promoter regions Nucleosome packing (euchromatin vs. heterochromatin) RNA interference (siRNAs) blocks transcription or translation, or can degrade existing mRNA

  12. Regulatory Proteins

  13. Regulatory Proteins

  14. Regulatory Proteins http://www.youtube.com/watch?v=P6Nyce-4oG4 (1:49) http://www.youtube.com/watch?v=WsofH466lqk (2:50) http://www.youtube.com/watch?v=vi-zWoobt_Q (3:37)

  15. Euchromatin vs. Heterochromatin

  16. siRNAs RNA folds back upon itself to form double stranded RNA (dsRNA) dsRNA is cut into small pieces (siRNAs) siRNAs bind to complimentary DNA sequences (that made the original RNA) to block RNA poly (stop transcription) siRNAs also inactivate mRNA by binding to it (complimentary sequences)

  17. siRNAs

  18. siRNAs http://www.youtube.com/watch?v=cK-OGB1_ELE (5:06)

  19. Bozeman Gene Regulation http://www.youtube.com/watch?v=3S3ZOmleAj0 (10:06) *if time

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