Regulation of gene expression in bacteria

Cards (42)

  • Transcription
    RNA synthesis from DNA template
  • Translation
    Protein synthesis from RNA template
  • Gene expression
    information in genes is converted into functional products/proteins
  • gene expression starts with
    Transcription
  • promoters
    binding of RNA polymerase at specific regulatory sites
  • Regulatory elements

    Cis-acting
  • regulatory elements

    upstream in bacteria/prokaryotes
  • regulatory elements

    present in mRNA and are essential for the process of translation
  • Translation
    ribosomal binding at 5’ untranslated regions and terminates the 3’ UTR
  • Bacteria
    Lacks spatial separation in transcription and translation
  • Eukaryotes
    have spatial separation both in transcription and translation
  • Levels of regulation in bacteria
    Transcriptional regulation
    Post-transcriptional regulation
    Translational regulation
    Post-translational regulation
  • Regulation in transcription
    Base pairs in -35 and -10 boxes that allow gene expression at different levels
  • gene expression is regulated in response to
    cell metabolic need
    various cellular process
    environmental conditions
  • Inducible control system
    bacterial cell induce the synthesis of enzymes
  • Lac operon
    Three enzymes; lac z, y and a
  • b-galactosidase
    converts disaccharide lactose into monosaccharide glucose and galactose
  • lac y
    encodes permease
  • Permease
    facilitates entry of lactose into the cell
  • Lac A
    encodes transacetylase
  • Transacetylase
    removes toxic by-products of lactose from the bacterial cell
  • How does lactose induce the expression of the lac operon?
    Gratituous inducer
    constitutive mutations
  • Gratitous inducer
    chemical molecule that doesn’t get metabolized by the products of the lac operon
  • Constitutive mutations
    mutations that allow continuous transcription of structural genes in bacterial operon
  • regulation of lac operon
    inducible because genes are only turned on when induced in the presence of lactose
  • If lactose is absent
    enzymes are not produced
  • Lac operon
    subject to negative control
  • Negative control
    transcription only occurs when repressor fails to bind to the operator region
  • Lac repressor
    Regulated by lac L gene
  • Lac L gene
    Constitutive gene(360 aas)
  • Lac l
    Produces an allosteric repressor
  • Allosteric repressor
    Reversible interaction that causes a change in the chemical activity and also a conformational change
  • Allosteric repressor has two active sites
    site that binds repressor to the DNA
    site that binds lactose to the repressor and induce and allosteric change
  • Lac Z
    Encodes B-galactosidase
  • Effects of Lac L gene mutations
    • Affect either/ both sites of the lac L gene
    • Alter the operator binding site of the repressor to prevent the binding of the repressor to the operator
    • Eliminate the inducer binding sites have the opposite effect.
    • Lack of the Lac L gene can also significantly promote lactose metabolism.
  • Merozygote
    generating a partially diploid organism
  • The Lac O gene and effects of its mutations
    Constitutive activation of the lac operon but not through the production of A.
    Altered operator sequence that can no longer interact with the repressor.
  • Cis-acting
    Operator
  • Transacting
    repressor
  • Cis-acting
    Affect activity of genes on which it is joined