MOL GEN LEC

• Gene Regulation


  A process where genes are turned on and off in different patterns during development to make a specific body cell look and act different from a different body cell
• Repressor


  Proteins that suppress transcription of a gene in response to an external stimulus
• Activator


  Proteins that increase transcription of a gene in response to an external stimulus
• Inducer


  Proteins that increase transcription of a gene depending on the needs of the cell and the availability of substrate
• Operon


  Units where proteins that share a metabolic pathway or are required for a certain function are encoded together
• If tryptophan is present in the environment, then E. coli does not need to synthesize it and the switch controlling the activation of the genes in the trp operon is switched on
• When tryptophan availability is low, the switch controlling the operon is turned off, transcription is initiated, the genes are expressed, and tryptophan is synthesized
• Catabolic Activator Protein (CAP)


  A protein that complexes with cAMP to bind to the promoter sequences of operons that control sugar processing when glucose is not available
• cAMP


  Molecule that begins to accumulate in the cell when glucose levels drop
• CAP Binding Sites (CBS) is located downstream of the RNA polymerase binding site in the promoter
• When cAMP is absent, transcription occurs at low rate
• CAP is a signaling molecule involved in glucose metabolism
• Binding of cAMP to CAP

  Occurs when glucose levels are low
• Lac Operon


  Will be turned on in high transcription when lactose is present and glucose is absent or limited
• Lac Repressor


  Indirectly sensed or detected allolactose
• There are 3 structural genes present in a lac operon
• Lactose, Allolactose, Galactose


  Utilized by the lac operon as alternative fuel sources for prokaryotes
• Gene regulation in prokaryotes occurs during transcription, not translation
• Regulators in the lac operon

  Lac Repressor and CAP
• The process of "turning off" a gene is called gene expression
• Gene expression is important for homeostasis, development, and specialization, but not for multicellularity
• The addition of methyl groups to cytosine causes genes to be turned off and transcription to be suppressed
• Metamorphosis


  The process of transformation from an immature form to an adult form that involves two or more distinct stages
• Control of gene expression in eukaryotes is more complex than in prokaryotes
• Nucleosomes


  Control the access of proteins to the DNA regions
• Acetylation of histones


  Causes conformational changes that turn on genes
• miRNAs


  Binding decreases the stability of RNA molecules
• Binding of transcription factors to enhancers

  Increases transcription of distant genes
• Post-transcriptional control mechanisms


  • Control of RNA splicing
  • Control of RNA stability
  • Control of RNA interference
• Mediator proteins


  Bring enhancers into contact with transcription factors and other proteins to increase transcription
• Alternative splicing


  Allows different products to be produced from one gene
• Cleavage and polyadenylation specificity factor

  Responsible for recognition of AAUAAA sequence as a signal for addition of adenines in 3' polyadenylation
• miRNAs were discovered in 1993 by Lee and colleagues in Caenorhabditis elegans
• Translational control


  Governs whether mRNA molecules in the cytoplasm are translated into proteins
• Protein degradation


  Targets proteins that are no longer needed or have become faulty
• Post-translational control


  Controls protein activity after the protein is synthesized
• Biochemical modification


  Addition of chemical groups after translation to activate protein function
• Proteolytic cleavage


  The process of breaking down proteins into smaller pieces which allows the polypeptide chain to fold and conform in the right ways that are required for activation
• COL E1 type plasmid replication is not unique to the bacteriophage family m13
• The Rolling Circle is a one-way process of plasmid replication