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Modern Genetic Analysis
14. Regulation of Gene Transcription
Key Concepts
Gene regulation is most often mediated by proteins that react to environmental signals by raising or lowering the transcription rates of specific genes.
In prokaryotes, coordinate gene control is achieved by clustering coordinated structural genes on the chromosome so that they are transcribed into multigenic mRNAs.
Negative regulatory control is exemplified by the lac system, in which a repressor protein blocks transcription by binding to DNA at a site termed the operator.
Positive regulatory control requires protein factors to activate transcription.
Many regulatory proteins have common structural features.
In eukaryotes, additional regulatory sites on DNA, such as enhancers, can act at considerable distance from the transcription start site to modulate gene expression by interacting with specific regulatory proteins.

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