Numerous mechanisms through which the specific product of a gene is controlled (ie. increasing or decreasing the amount of genetic product formed).

Eukaryotes Edit

18 01 gene expression-L

Gene expression in eukaryotes is controlled by numerous factors within the cell that alter either the transcription of DNA (including the splicing of exons in the pre-processed mRNA, the degradation of mRNA by enzymes, & the rate of protein production) or create chemical modifications to the protein product such as phosphorylation or methylation.[Gene Regulation 1]

DNA Methylation Edit

DNA Methylation is the process in which gene expression is regulated by modifying cytosines, thus causing a silencing of genes due to the addition of methyl groups to cytosines and histones.

Bacteria and Bacteriophages Edit

Gene expression and regulation in bacteria and bacteriophages is controlled primarily by operons. These operons will either have positive or negative controls which will regulate the amount of product being produced by the specific gene that is being translated.[Gene Regulation 2]

Positive Control Edit

This type of regulation can be seen in the lac operon of E.coli, in which lactose must be present and glucose must be absent. With these conditions met, CAP must interact with cAMP in order for the CAP-cAMP complex to form and bind to the CAP site on the operon to create the activation signal necessary for the RNA polymerase to bind to the promoter within the lac operon and begin the process of mRNA transcription and translation.

Negative Control Edit

This type of regulation can be seen in the trp operon of E.coli, which requires the presence of tryptophan in order for the trp repressor present on the operator (which normally blocks the initiation of transcription) to be activated and release from the trp operon.

The lac operon also illustrates negative control due to the lac repressor protein that blocks RNA polymerase from binding to the operator. The presence of allolactose, an isomer of lactose, is needed in order for the allolactose to bind to the lac repressor and release the complex from the operator; RNA polymerase may then bind to the operon and begin transcription.[Gene Regulation 3]

References Edit

  1. Russell, Peter J. "Regulation of Gene Expression in Eukaryotes." IGenetics: A Molecular Approach. San Francisco: Benjamin Cummings, 2010. 518-41. Print.
  2. Russell, Peter J. "Regulation of Gene Expression in Bacteria and Bacteriophages." IGenetics: A Molecular Approach. San Francisco: Benjamin Cummings, 2010. 491-512. Print.