Regulatory elements can be used for either positive and negative transcriptional control. When a gene is subject to positive transcriptional control, the binding of a specific transcription factor to the regulatory element promotes transcription. When a gene is subject to negative transcriptional control, the binding of a specific transcription factor to a regulator elements represses transcription. A single gene can be subject to both positive and negative transcriptional control by different transcription factors, creating multiple layers of regulation.
The lac operon in E. coli is a classic example of a prokaryotic operon which is subject to both positive and negative regulation. Positive regulation and negative regulation are universal themes for gene regulation in both prokaryotes and eukaryotes.
Chapter 10: Regulation of Gene Expression Essay | …
Often different types of cells in different tissues express different splice variants of the same gene, such that there is a heart-specific transcript and a kidney-specific transcript of a particular gene.
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If you understand the similarities and differences in eukaryotic and prokaryotic gene regulation, then you know which of the following process are exclusive to eukaryotes, which are exclusive to prokaryotes, which occur in both, and how each is accomplished:
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In general, eukaryotic gene regulation is more complex than prokaryotic gene regulation. The upstream regulatory regions of eukaryotic genes have binding sites for multiple transcription factors, both positive regulators and negative regulators, that work in combination to determine the level of transcription. Some transcription factor binding sites, called enhancers and silencers, work at quite a distance, thousands of base pairs away from the promoter. Activators are examples of positive regulation and repressors are examples of negative regulation.
The Process and Purpose of Gene Expression Regulation
These are DNA sequences that preceede a transcription unit that need to have specific proteins present for RNA polymerase to begin transcription.
The proteins that mediate RNA Polymerase are known as "
Control of transcription factor availability is one of the major ways that cells of a multicellular organism accomplish "
differential gene expression
", which in turn allows cells to "
" to serve different functions in the organism.
This is crucial!!!
So many options lead to so many outcomes.
are necessary for eukaryotic mRNA to remain functional and be transported to the cytoplasm for translation.
" of exons allows for multiple functional (or non-functional) gene products to be made from a single primary transcript.
Anywhere from 75 - 100 percent of human genes with multiple exons probably undergo alternative splicing.
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Another difference between prokaryotic and eukaryotic gene regulation is that eukaryotic mRNAs must be properly processed with addition of the 5′ cap, splicing out of introns, and addition of the 3′ poly(A) tail (discussed in more detail ). Each of these processing steps is also subject to regulation, and the mRNA will be degraded if any of them are not properly completed. The export of mRNAs from the nucleus to the cytoplasm is also regulated, as is stability of the properly processed mRNA in the cytoplasm.