An operon is a sequence of DNA containing a cluster of genes under the control of a single promoter
- Hence, genes within an operon will always be expressed together or not at all (their expression patterns are linked)
There are three basic components to an operon
- Promoter – Upstream sequence to which RNA polymerase binds
- Operator – Segment of DNA to which a repressor protein binds (inhibits transcription by obstructing RNA polymerase)
- Structural genes – Genes that are collectively regulated by the operon
Operons are related to stimulons and regulons:
- Stimulon – Set of genes under regulation from a single cell stimulus
- Regulon – Set of genes under regulation from a single regulatory protein (each gene has a different operator though)
Originally, operons were thought to exist only in prokaryotes, however examples have since been found in eukaryotes
Structure of an Operon
Promoters are sequences of DNA that tell RNA polymerase and transcription factors to bond to the DNA and begin transcription. A promoter is an area of DNA where transcription
of the DNA begins. The promoter controls the expression of the gene by signaling to RNA polymerase to begin transcription and the direction in which the polymerase should transcribe the DNA.
Genes express themselves by forming proteins . Operators are where transcription factors bind to the DNA to prevent transcription.Key Questions
Through Transcription , the information of gene is carried onto the mRNA which on Translation produces proteins. This protein can be Structural , or Enzyme or Hormone and thus the gene expresses itself.
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