Expression Regulation

Cards (34)

  • Gene regulation
    Mechanisms for controlling which genes get expressed at which levels
  • Operon
    Cluster of genes under control of a single promoter (all transcribed together) which usually have functions that work together so will have to happen at the same time anyways. Common in prokaryotes but rare in eukaryotes
  • Regulatory protein
    Proteins that control how much of an operon is transcribed
  • Inducer
    Small molecule capable of turning operons "on" from their usual "off" state
  • Corepressor
    Small molecule capable of turning an operon "off"
  • Housekeeping genes
    Genes whose products are constantly needed by the cell to maintain essential functions. Have promotors and other regulatory DNA sequences that ensure constant expression
  • Lac operon
    Operon that allows bacteria to use lactose as a fuel source when glucose is unavailable
  • Operator
    Overlaps the lac promoter so that when it is there, RNA polymerase cannot bind to it, and so negatively regulates its use
  • CAP binding site
    Positive regulator site bound by catabolite activator protein which helps RNA polymerase attach to transcribe proteins when bound
  • Lac repressor
    Protein that inhibits the transcription of the lac operon by binding to the operator, which overlaps the promotor. When lactose is present, it loses its ability to bind and floats off, leaving it technically open for transcription
  • Allolactose
    Isomer of lactose that is synthesized in small numbers when lactose is present. Inducer that changes the lac repressor shape so that it can no longer bind DNA
  • Inducer
    Small molecule that triggers the expression of a gene or operon
  • Inducible operon

    Operons that are usually repressed but can be turned on with the presence of an inducer (like the lac operon with allolactase)
  • Catabolic activator protein
    CAP
  • CAP
    Protein that binds to a region of DNA just before the promoter region that helps guide RNA polymerase attach to it, driving high levels of transcription. Necessary in the lac operon because it's not usually transcribed on its own
  • CAP is generally produced in low glucose environments, because it needs cAMP to bind to the DNA. However, when glucose is high, there is less cAMP, so that's why the lac operon (which needs CAP to catalyze more transcription) only kicks in when there is low glucose and lactose available
  • cAMP
    Hunger signal made by e coli when glucose levels are low. Needed to bind to CAP to activate the lac operon
  • trp operon
    E coli operon used to synthesize its own tryptophan when it's not available in its environment
  • Corepressor
    Small molecule like tryptophan that puts a repressor in its active state
  • Attenuation
    Mechanism for reducing expression of the trp operon by stopping it from completing translation, even after it's been initiated, when tryptophan levels are high enough
  • Chromatic accessibility
    Type of gene regulation where more relaxed chromatin is easier to transcribe than more tightly wound chromatin
  • Transcription
    Key regulatory point for many genes where the available transcription factors for specific genes could repress or increase their expression
  • RNA processing
    Gene expression regulation that involves different RNAs being made from the same RNA through alternative splicing
  • RNA stability
    Gene expression factor that has to do with how long an mRNA floats in the cytosol relating to how many proteins can be synthesized from it. miRNAs play a role too because they can chop up mRNAs if they're excessive
  • Translation
    Gene expression factor that has to do with how much an mRNA is turned into proteins. Influenced by regulators that can increase it or decrease it
  • Protein activity
    Gene expression factor that has to do with how a protein acts after it's been synthesized (like if it's been tagged or chopped up)
  • Transcription factors
    Proteins that help turn genes "on" or "off" by binding to nearby DNA
  • Basal transcription factors
    Part of a eukaryotic cell's core transcription toolkit which is needed for RNA polymerase to attach to the promoter on the gene's DNA
  • Activators
    Transcription factors that make transcription happen, like by helping basal transcription factors and/or RNA polymerase bind to the promoter
  • Repressors
    Transcription factors that inhibit transcription, like by getting in the way of RNA polymerase and/or basal transcription factors so they can't get to promotors and begin transcription
  • Binding sites for transcription factors can sometimes be far from the promotor because DNA loops back on itself and folds so that they're essentially next to each other anyways
  • A gene that has to be expressed in more than one body part or cell type will probably have enhancers to activate where it needs to be activated and silencers for the opposite
  • Tissue specific enhancers

    Enhancers that control a gene's expression in certain parts of the body. Mutations in these cause changes in body form, whereas mutations in the gene itself would probably be fatal
  • Combinatorial regulation
    When a gene is controlled by several transcription factors, and so needs several conditions to turn on, like an actual coding logic system. Foe example, only if activators A and B are present but repressor C is absent