Regulation of gene expression

Created March 2020, Offline version here
Video by Paul Anderson, also on his website Bozeman Science.


    Gene regulation describes the process through which the of genes is controlled.
    Gene regulation involves the actions of regulatory sequences and proteins. An example of a regulatory sequence is a .
    When the relevant factors bind regulatory sequences, RNA polymerase can bind and transcribe the DNA into .
    In E. coli, genes that are active in the same pathway are organized into clusters called .
    A regulatory sequence called an lies between the promoter and the genes, acting like an on/off switch
    The lac operon is a well-studied example of gene regulation in which the of lactose can be heavily controlled.
    When is not present, a regulatory protein called a repressor binds to the operator, preventing the binding and activity of RNA polymerase.
    As a result of RNA polymerase being unable to bind, the gene is off. When lactose is present, the lactose can bind to the repressor and cause that means the repressor is released from the operator.
    When the repressor is released from the operator, the genes required to breakdown lactose can be transcribed by
    Gene regulation by the lac operon is an example of regulation.
    The trp operon contains genes that encode proteins required for the synthesis of tryptophan, which is .
    The trp operon is in the “off” state in the presence of tryptophan, which is an example of gene regulation.
    This is because if tryptophan is present in the environment, the cell will not want to waste resources making the proteins to synthesize it. The trp molecule binds to the repressor, protein causing a change in its that allows the repressor to bind to the operator and RNA polymerase.
    In the absence of tryptophan, the cell needs to tryptophan to continue making proteins.
    The lack of tryptophan in the environment means than no tryptophan molecules are bound to the repressor protein, allowing its release from the .
    This allows the genes in the trp operon to be transcribed by RNA polymerase, and tryptophan to be synthesized when it is required by the cell.
    The control of gene expression in organisms like animals and plants is in bacteria
    In ,genes are not organized into operons.
    Instead, the coordinated binding of proteins called controls the expression of individual genes.
    The binding of transcription factors causes RNA polymerase to bind at the promoter, but also its attachment to permit the transcription of a gene by RNA polymerase, the DNA has to change