Vocabulary

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Vocabulary

• Positive gene control
• Negative gene control
• Lac Operon
• Trp Operon
• Plasmid
• Transformation
• Conjugation
• Retrovirus
• Lytic cycle
• Lysogenic cycle

• Operon
• Inducible and repressible
• Promoter
• Terminator
• Enhancer
• Regulatory Gene
• Inducer
• Repressor
• Regulatory Protein/Sequence

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• operator switch that controls access of RNA
  polymerase to genes for transcription
• repressor a protein that binds to the operator
  to block transcription
• corepressor small molecule that binds to
  repressor to make it active (helps block
  transcription)
• regulatory gene gene that code for the
  production of repressors (always on at a low
  rate)
• Regulatory sequence stretch of DNA that
  interacts with regulatory proteins to control
  transcription (promoter, terminator, enhancer)
• inducer small molecule that inactivates the
  repressor (allows transcription)

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Gene ExpressionBiotechnologyBacteria and Viruses

• Chapters 18, 19, and 20

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• Genes regulated at the transcription stage
  (mostly).
• feedback inhibition (positive and negative)
• Important in embryonic development (eukaryotes)
  to create differentiated cells
• Also important in cancer prevention and
  regulation of the cell cycle
• There are differences in the way prokaryotes and
  eukaryotes regulate gene expressionwhy??

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Prokaryotic Gene Regulation

• Express only those genes that are needed by the
  cell (allows for efficient metabolism)
• Adjust activity of enzymes
• Adjust production level of enzymes
• Genes switched on/off as needed due to
  environmental conditions
• Operon model basic mechanism for the control of
  gene expression in bacteria

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Operons

• Operon entire stretch of DNA required to produce
  a protein (enzyme)under the control of a single
  promoter
• this may include several genes
• operator promoter genes
• Negative Gene Regulation (operon switched off by
  repressor)
• Lac operon (inducible)
• Trp operon (repressible)

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Lac Operon

• inducible operon. usually off but can be turned
  on by allolactose (sugar--isomer of lactose)
• inactivates repressor to allow for transcription
• genes code for 3 enzymes that utilize lactose
• Figures 18.4(a) and 18.4(b)

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Trp Operon

• repressible operon. controls synthesis of
  tryptophan (amino acid)
• is usually on, but can be switched off by a
  repressor. (prevents transcription)
• controlled by a regulatory gene (trpR). (always
  expressed at a low rate)
• allosteric regulation!
• Increased concentration of tryptophan will result
  in less of it synthesized by bacteria
• Figures 18.3(a) and 18.3(b)

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• Positive gene regulation (regulatory protein
  interacts directly with genome to switch
  transcription on)
• Positive feedback!
• Cyclic AMP (cAMP) and Lac operon
• bacteria preferentially use glucose for energy
  (glycolysis) but will use lactose in its absence
  (lac operon switches on)
• cAMP accumulates when glucose is scarce
• enhances the production of enzymes from the lac
  operon (directly stimulates gene expression)
• Binds to specific region in promoter
• also has the ability to enhance the transcription
  of other genes (not just lac)

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Bacteria

• Three shapes (cocci, bacilli, spirilla)
• Gram and Gram-
• Cell wall type
• lack complex compartmentalization (prokaryotes)
• circular chromosome located in nucleoid (region
  of cytoplasm)

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• Plasmids (independently replicating DNA carrying
  few genes)
• R plasmid (carries resistance genes for specific
  antibiotics)

-MRSA (methicillin resitance) -Multi-drug
resistant strains -Enterococcus sp.
-Pseudomonas sp. -Tuberculosis Implications
for human and veterinary medicine, as well as
agriculture
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Bacterial Reproduction

• No sexual reproduction
• asexual (binary fission)
• New mutations increase genetic diversity rapidly
  due to short generation times (rapid evolution)

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Bacterial Reproduction

• Horizontal Gene Transfer
• Transformation (take in foreign DNA from its
  surroundings)
• produces recombinant cells (DNA from two
  different cells)
• Transduction (bacteriophages--viruses carry genes
  from one cell to another)
• recombinant cells produced
• Conjugation (DNA transferred between two
  cells--one cell donates the other receives)
• Transposition (DNA segments move with and
  between molecules)
• jumping genesmove from chromosome to plasmid

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Eukaryotic Gene Regulation

• No Operons!!
• Differential gene expression different genes
  expressed by cells within the same genome
• Depends on cell function or stage of development
• Like prokaryotes, most often regulated at the
  stage of transcription (but much more complex)
• Eukaryotes do have the ability to control gene
  expression at every step of the process

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How it works
http//www.bozemanscience.com/031-gene-regulation/

• Transcription factors need to be present for the
  process to begin
• These bind to specific DNA sequences upstream
  of the gene to be expressed (regulatory
  regionsenhancer/promoter)
• Attracts RNA polymerase to attach
• Controlling availability of these factors in a
  cell is a major component in regulating gene
  expression
• Some factors are activators (increase expression)
  others are repressors (decrease expression)
• These determine what (or if) genes will be
  expressed (and how much)
• This changes phenotype of the organism!

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Applications to Biotech

• Plasmids can be used to genetically engineer
  organisms, also to further study specific genes
• Easily moved between organisms, easily
  manipulated
• restriction enzymes (restriction endonucleases)
  are used to cut DNA at specific sequences
  (restriction sites)
• Produces blunt or sticky ends (depends on cut)
• Hundreds have been identified, each recognizes a
  specific site
• EcoR1 cuts at GAATTC

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• DNA (cut with the same enzyme) is then combined
  with other DNA making a recombinant DNA sequence
• Base-pairing occurs, ligase seals break
• This can produce some very interesting organisms!
  It allows for cells to produce proteins they
  wouldnt normally.
• Insulin, vaccines, oil spill clean up,
  agriculture, etc.

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Technologies (electrophoresis)
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Gene Expression and Development
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Gene Expression and Cancer
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Viruses

• Retroviruses
• Lytic cycle
• Lysogenic cycle
• Transduction and transposons
• Examples.